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For Use in Horseback Riding

Special Note to Helmet Users

            There are four reasons for you to be interested in this Standard:

1.         Horseback riding imposes risks of death or permanent impairment due to head injury.

2.         The proper use of protective helmets can minimize the risk of death or permanent impairment. 

3.         The protective capacity of a helmet is difficult to measure, particularly at the time of purchase or use.

4.         Snell certification backed by ongoing random sample testing identifies those helmet models providing and maintaining the highest levels of head protection.

            There are at least four critical elements affecting a helmet's protective properties:

1.         Impact management - how well the helmet protects against collisions with large objects.

2.         Helmet positional stability - whether the helmet will be in place, on the head, when it's needed.

3.         Retention system strength - whether the chinstraps are sufficiently strong to hold the helmet throughout an incident involving head impact.

4.         Extent of Protection - the area of the head protected by the helmet.

            This Standard describes simple tests for all four of these items.  However, the tests for the second item, helmet stability, of necessity presume that the helmet is well ``matched to the wearer's head and that it has been carefully adjusted to obtain the best fit possible.  Unless you take similar care in the selection and fitting of your own helmet, you may not obtain the level of protection that current headgear can provide.

            The Foundation recommends the simple, straightforward procedure recommended to consumers by most helmet manufacturers:

            Position the helmet on your head so that it sits low on your forehead; if you can't see the edge of the brim at the extreme upper range of your vision, the helmet is probably out of place.  Adjust the chinstraps so that, when buckled, they hold the helmet firmly in place.  This positioning and adjusting should be repeated to obtain the very best result possible.  The procedure initially may be time consuming.  Take the time.

            Try to remove the helmet without undoing the chinstrap.  If the helmet comes off or shifts over your eyes, readjust and try again.  If no adjustment seems to work, this helmet is not for you; try another.

            This procedure is also the basis of the test for helmet stability described in this Standard.  This test performs the same steps but uses standard head forms. 

            However, you must still perform this procedure for yourself when buying a helmet and every time you wear a helmet.  Only in this way will you be able to make all the proper adjustments in pads and strapping to get the best fit possible.  Furthermore, your test on your own head will be an improvement on ours; you will determine whether the helmet is appropriate for you personally.

            There are several other important aspects of helmets to consider.  Bright colors and reflective patches will make you more visible to others and therefore less likely to be involved in a collision.


            In a riding accident, the rider may suffer injury or death.  Helmets on the market today offer varying degrees of protection, but the consumer has little basis for judging the relative effectiveness of a given model.  This Standard presents a rational means for differentiating between helmets which meet specified standards for impact protection and retention system effectiveness and those which do not.

            The Snell Foundation urges that protective helmets be required for all individuals participating in supervised equestrian events and encourages the riding public in general to wear helmets which meet appropriate performance standards[1].

            This 2016 Standard establishes performance characteristics suitable for horseback riding.  This Standard does not establish construction and material specifications.  The Foundation does not recommend specific materials or designs.  Manufacturers submit helmets to be tested under this Standard and if the submitted helmets pass, a certification is issued.

            The Foundation will make available the identity of those products which have been Snell certified but will not attempt to rank those products according to performance or to any other criteria.  Neither does the Foundation distinguish between the needs of participants in competitive events and those of the general riding public.

            All of the requirements described herein, including both initial certification and random sample testing, are an integral part of this Standard.  No helmet can satisfy the Standard unless it is subject to both certification and random sample testing by the Foundation.

            Snell certification for protective headgear requires a specific contractual agreement between the primary headgear manufacturer and the Foundation.  Certification procedures may be obtained upon application to the Foundation.


            This Standard addresses the problem of protecting the head from direct impact with various shapes of surfaces that may be encountered in a riding accident.  The Standard prescribes direct measures of several factors bearing on a helmet's ability to protect the head as well as its general serviceability as equestrian headgear.  Thus, this Standard is directed towards the kinds of performance bearing on head protection that may not readily be discernible by even knowledgeable consumers at the time of purchase.

            Some of these performance requirements have been expressed in terms of limitations on the various components and features of the single general helmet configuration currently available.  These expressions have been used only for the sake of clarity and should not be misinterpreted as requiring specific configurations or materials.  As newer helmet technologies appear, these limitations will be re-examined and, perhaps, restated.

            An equestrian helmet consists generally of a rigid head covering and a retention system composed of flexible straps and hardware.  The rigid covering protects the head from direct impact by its capacity to manage impact energy and also by its capacity to spread a concentrated load at its outer surface over a larger area of the wearer's head.

            The retention system holds the headgear in position throughout normal usage and especially during falls and accidents.  This Standard applies two different tests to the retention system.  The first of these tests for stability by fitting the headgear to a standard head form and then attempting to displace it by applying tangential shock loadings.  The second tests retention system strength by applying a shock load to the system components through a simulated chin.

            The quality of the fit and the care taken with the adjustments are absolutely critical elements in these tests.  The manufacturer must provide suitable guidance so that the wearer will be able to select and adjust headgear to obtain the necessary quality of fit and positional stability.

            The capacity for impact protection is determined by direct measurement of the shock delivered through the helmet to a head form when the helmeted head form is dropped in a specified manner onto any of three unyielding anvils.  One of these anvils, the horse shoe anvil, also tests the helmet's ability to resist penetration by a sharp edged, horse shoe like object.  The impacts against the horse shoe anvil may approach the severities of falls but in no way approximate the power of a kicking horse.  Protection from kicks is doubtful. 

            The helmet must also meet requirements for rigidity in order to provide some measure of protection against crushing injuries to the head.  The helmet is compressed laterally between two parallel cylindrical bars.  The helmet must withstand a prescribed level of compressive force for a given period of time.  The helmet's peak lateral deformation must not exceed a prescribed value.  

            Most equestrian helmets are intended to accommodate a range of head sizes and shapes.  Various thicknesses of resilient lining material may be placed within otherwise identical helmets during production to configure the fit to several different ranges of head size.  This resilient padding does not significantly affect the way the helmet absorbs and attenuates impact and is not directly addressed in this Standard.

            Other general features of equestrian helmets may include eyeshades, bright colors and reflective surfaces.  These features all deal with matters of safety and comfort that are not directly addressed in this Standard but which merit the consideration of wearers as well as manufacturers.

            Although equestrian helmet use has been shown to reduce head injuries significantly, there are limits to a helmet's protective capability.  No helmet can protect the wearer against all foreseeable accidents.  Therefore, injury, death or permanent impairment may occur in accidents which exceed the protective capability of any helmet including even those helmets meeting the requirements of this Standard.

            A helmet's protective capability may be exhausted in an accident.  Helmets are constructed so that the energy of a blow is managed by the helmet, which may cause its partial or total destruction.  Because the damage may not be readily apparent, the Foundation strongly recommends that a helmet impacted in an accident be returned to the manufacturer for complete inspection.  If it is not possible to return the helmet, the helmet should always be destroyed and replaced.

            Finally, the protective capability may diminish over time.  Some helmets are made of materials which deteriorate with age and therefore have a limited life span.  At the present time, the Foundation recommends that equestrian helmets be replaced after five (5) years, or less if the manufacturer so recommends.

            The remainder of this Standard is divided into sections on construction, qualifications for certification, modifications, random sample testing, labelling and marking, extent of protection, and testing.  The section on qualifications for certification discusses helmets submitted for the Foundation's certification program.  Construction, extent of protection and testing describe the requirements that helmets must meet to be admitted to the Foundation's program.  These sections plus the sections on random sample testing, labelling and marking, and modifications describe the requirements that helmets must meet to continue in the Foundation's program.


A.  General

            The assembled helmet shall have smooth external and internal surfaces.  Any feature projecting more than 5 mm beyond the outer surface must readily break away; all other projections on the outer surface shall be smoothly faired and offer minimal frictional resistance to tangential impact forces.  There shall be no feature on the inner surface projecting more than 2 mm into the helmet interior.  The helmet shall provide as nearly uniform impact protection over the entire protected area as is practicable.

            If the absence of any detachable component of the helmet does not prevent its being worn, then this absence must not compromise either the retention system or the impact protection.  If any part of the helmet detaches during testing, it must offer no laceration or puncture hazard nor reduce the area of coverage of the head.

            If the manufacturer provides add-ons such as visors, face shields and neck curtains with the helmet, these add-ons must neither lessen the protective capability of the basic helmet nor create a direct hazard for the wearer.

B.  Materials

            Ideally, materials used in the manufacture of the helmet should be of durable quality and not be harmed by exposure to sun, rain, dust, vibration, sweat or products applied to the skin or hair.  Similarly, the materials should not degrade due to temperature extremes likely to be encountered in routine storage or transportation. 

            Materials which are known to cause skin irritation or are conducive to disease shall not be used for the parts which contact the skin.  Materials that support the growth of fungi or algae shall not be used.  Lining materials, if used, may be detachable for the purpose of washing. 

C.  Finish

            All edges of the helmet shall be smoothed and rounded with no metallic parts or other rigid projections on the inside of the shell that might injure the wearer's head in the event of impact.

D.  Retention System

            The retention system shall be designed so as to discourage misuse.  That is, of all the ways in which the retention system might be used, the design use shall be the simplest and quickest to implement.  Helmets shall not be fitted with "non-essential" features which, if misused, can degrade the performance.  Quick release buckles, if used, shall not be able to be released inadvertently.

E.  Peripheral Vision

            The helmet shall provide peripheral visual clearance.  This clearance is defined using a reference head form appropriate to the size of the helmet and corresponds to a visual field of at least 105° to the right and to the left of straight ahead.

            The helmet shall also provide an upward visual clearance.  This clearance is defined using a reference head form appropriate to the size of the helmet and corresponds to a visual field of at least 7° upward from horizontal.

                                              QUALIFICATIONS FOR CERTIFICATION

            For qualification testing, helmets shall be in the same condition as those offered for sale.  No helmet or component which has been subjected to any tests described in this Standard shall be offered for sale after testing.  At least six (6) complete helmets and as many as eight (8) must be submitted by the manufacturer for a certification test program for each size of this model offered for sale.  All but one of these samples will be destroyed in testing; the untested sample shall be retained for comparison and reference.


            Cosmetic changes to certified headgear are permissible.  Such changes are generally limited to marking or trimming the headgear with manufacturer approved paint or tape.

            Otherwise, modification of certified headgear creates new headgear which will not have the confidence and certification of the Foundation until samples have been submitted and evaluated.  Manufacturers must not place the Foundation's certification label in any modified headgear for which they have not received written permission.

            After-market modifiers of such certified headgear should be aware that any structural modification may adversely affect a helmet's protective capability and therefore invalidate the certification. 

                                                         RANDOM SAMPLE TESTING

            In addition to the certification testing, the Foundation will routinely obtain and test samples of previously certified models.  These samples will be selected from among those stocks intended for retail sale to consumers.  In this manner, the Foundation will attempt to ensure that the helmets made available to the public continue to meet the performance requirements of this Standard.

            In cases in which helmets are provided directly to users and do not pass through a normal sales distribution system, the Foundation will set up alternative procedures to monitor certified products.  Specifically, if helmets are provided directly to teams or individuals for use in organized events, the Foundation must have access to the helmets for spot checking and non-destructive evaluation.


                                                           LABELING AND MARKING

            Each helmet shall have durable, visible and legible labeling identifying the manufacturer, the month and year of manufacture, the model and the size.  Labeling shall be uncoded and either in English or a language common to the area where the helmets are to be distributed.  The headgear shall also be labeled to the following effect:

                        1.         Certified for equestrian use only.

                        2.         No helmet can protect the wearer against all foreseeable impacts.  However, for maximum protection, the helmet must be of good fit and all retention straps must be securely fastened.  The helmet, when fitted and fastened, shall resist any inadvertent dislodgement or removal.

                        3.         This helmet is so constructed that the energy of an impact may be absorbed through its partial destruction, though damage may not be visible.  If it suffers an impact, it must either be returned to the manufacturer for inspection or be destroyed and replaced.

4.         Intended for head circumferences from XX cm through YY cm. (XX and YY represent numerical values for the smallest and largest head circumferences for which the helmet is intended.)

            If any of the helmet components are sensitive to common solvents, adhesives, paints or cleansers; the helmet must also bear labels to the following effect:

            This helmet can be seriously damaged by some common substances without visible damage.  Avoid contact with: (List damaging fluids, etc.)  Apply only the following:  (Recommended cleaning agents, paints, adhesives and the like) as appropriate. 

            Each helmet shall also include one of the Foundation's serialized certification labels.  The Snell certification label shall be placed either inside or on the outside of the helmet, as appropriate, in such a way that it cannot be removed intact.

            The registered trademark (certification label) of the Snell Memorial Foundation may be used by the manufacturer only under license from the Snell Memorial Foundation.  The specifics of licensure may be obtained from the Foundation.

 Figure 1 ISO Head Form – ISO DIS 6220-1983


            This standard invokes six standard head forms for helmet inspection, marking and testing.  The geometry of these head forms is according to the definitions for the ‘A’, ‘C’, ‘E’, ‘J’, ‘M’, and ‘O’ head forms described in International Standards Organization (ISO) Draft Standard ISO DIS 6220-1983.  The impact mass specifications for the impact test phase are comparable to those in ECE 22-05 for these same head form designations.

            ISO DIS 6220-1983 includes descriptions for half head forms suitable for guided fall impact testing or for full head forms such as those used in the positional stability tests.  Figures 1 and 2 depict the general shapes of the half head form configuration.  The following table lists useful dimensions from the two references given above.

Table 1 Useful Head Form Parameters

Head Form


Total Mass

(entire drop assembly)

Crown to Basic Plane

Basic to Reference Plane


50 cm

3.100 kg ± 100 g

113.5 mm

24.0 mm


52 cm

3.600 kg ± 100 g

118.0 mm

25.0 mm


54 cm

4.100 kg ± 100 g

122.0 mm

26.0 mm


57 cm

4.700 kg ± 100 g

130.0 mm

27.5 mm


60 cm

5.600 kg ± 100 g

136.0 mm

29.0 mm


62 mm

6.100 kg ± 100 g

140.0 mm

30.0 mm



            The extent of protection corresponds to that region of the head for which protection is sought. 

            There are a number of planes fixed in the geometry of these head forms as shown in Figure 1.  This description of the extent of protection uses the ISO definitions of the basic plane, the longitudinal plane, the transverse plane and the reference plane.  Other planes have also been defined strictly for convenience and clarity.

            The basic plane corresponds to the anatomical plane (Frankfort plane) that includes the auditory meatuses and the inferior orbital rims.  The reference plane is above and parallel to the basic plane. The longitudinal or mid-sagittal plane is perpendicular to the basic plane and is the plane of symmetry dividing the right half of the head form from the left.  The transverse or coronal plane is perpendicular to both the longitudinal and basic planes.  It corresponds to the anatomical plane that contains the two auditory meatuses and divides the front from the rear portions of the head.

            These planes are all well-known entities.  Several other planes, however, have proven useful.  The S0 and S3 planes are parallel to the basic plane and lie above or below it at distances determined by the size of the head form.  The rear plane divides the rear third of the head from the front two thirds.  It is parallel to the transverse plane and lies at a given distance behind the point where the reference plane and longitudinal planes intersect with the front surface of the head form.  The distance from this point, hereafter called the reference point, is determined by the size of the head form.  The fore plane is also parallel to the transverse plane.  It lies behind the reference point at a distance determined by the size of the head form.


Figure 2 Extent of Protection


Table 2 Extent of Protection

Head form









39.0 mm

128.6 mm

26.1 mm

46.8 mm

52.2 mm


40.6 mm

133.8 mm

27.2 mm

48.4 mm

54.3 mm


42.2 mm

139.0 mm

28.2 mm

50.0 mm

56.4 mm


45.2 mm

148.4 mm

30.0 mm

53.0 mm

60.0 mm


47.4 mm

155.8 mm

31.5 mm

55.2 mm

63.0 mm


49.2 mm

161.5 mm

32.2 mm

57.2 mm

64.5 mm


            The extent of protection provided by the helmet must include the entire region above the S0 plane and forward of the fore plane, the entire region above the S3 plane and between the fore and rear planes and the entire region above the S4 plane and behind the rear plane.  Figure 2 and the associated table lay out these additional defined features and show the extent of protection and the test line.


A.  Inspection

            Each helmet will be inspected for the required labels and for compliance with the general limitations made on structure.  The weight and various circumferences will be recorded for comparison with other samples of the same make and model.

            Some helmets may incorporate innovations and other features not anticipated by this Standard but which raise concerns about the safety and effectiveness of the headgear.  These will be referred to members of the Foundation's Board of Directors for evaluation.  Any feature found to reduce the protective capacity of the headgear, whether explicitly mentioned in this Standard or not, will be a cause for rejection.

B.  Head Forms and Helmet Positioning

            The determination of which head forms are appropriate to a helmet is based on the specified smallest and largest head circumferences for the helmet.  For samples submitted for certification, this specification must include the smallest and largest values of head circumference for every possible fit pad configuration of the helmet.  For helmets received for RST testing, the smallest and largest head circumferences will be taken directly from the helmet label.

If the smallest head circumference specified for the helmet is less than 50 cm, the A head form is the smallest appropriate.  Otherwise, the smallest appropriate head form for a particular helmet is the largest of the six head forms whose circumference is no greater than the manufacturer’s specified smallest circumference. The largest appropriate head form is the largest of the six specified head forms whose circumference is no greater than the manufacturer’s specified largest circumference.

Table 3 Test Head Forms as Determined by Size Specification



Largest Size Specified

50 - 51

52 - 53

54 - 56


60 - 61


Smallest Size Specified












































If the test samples are determined to be too small to accommodate the largest head form identified as appropriate, the next smaller head form shall be considered the largest appropriate.  If the samples are too small for even the smallest appropriate head form as indicated by the manufacture specification, the samples shall be rejected for certification.

The table shows which head forms will be used in certification testing for various head size specifications.  Since the largest head size should never be smaller than the smallest head size, most of the lower left region of the table is blank. 

If the size specification corresponds to one of the gray cells along the table’s main diagonal, only a single test head form will be necessary and the manufacturer need only submit five samples identical samples configured with comfort padding for the largest intended head size for certification testing.  Otherwise, two more samples are required, identical to the first five in all respects except that the comfort padding must be configured for the smallest intended head size.

            During testing, helmets will be positioned on the selected test head form according to the manufacturer’s specified helmet positioning indices.  If the manufacturer fails to provide positioning information with certification samples, the helmets will be positioned according to the best judgment of the authorized technical personnel.  If the helmets meet certification requirements, the helmet positioning indices will be those used in all future testing.

            These helmet positioning indices represent distances on the front of the head form from the basic plane along the intersection with the longitudinal plane upward to the lower brow edge of the helmet.  Helmet positioning indices will be assigned for all head form sizes appropriate to the headgear.  Each headgear could conceivably require as many as six helmet positioning indices, one each for the ‘A’, ‘C’, ‘E’, ‘J’, ‘M’ and ‘O’ head forms.

C. Marking

            The helmet is placed upon the largest appropriate ISO head form, positioned according to the apposite helmet positioning index and held in place with an applied force of 50 newtons (11.25 lbs).  The intersections of the shell with the various defined planes are then traced onto the outer surface of the helmet in the following manner:

            The level of the S0 plane is marked on that portion of the helmet in front of the fore plane.  The level of the S3 plane is marked on that portion lying between the fore and rear planes.  The level of the S4 plane is marked on that portion behind the rear plane.  Finally, line segments along the fore plane are marked to join the S0 and S3 planes and, similarly, line segments along the rear plane are marked to join the S3 and S4 planes. 

            These lines enclose the top of the helmet and are the boundary of the required extent of protection.  A test line shall be drawn within this extent of protection so that it is 15 mm from the closest point on the boundary.  (See Figure 2)

            If identical helmets are to be configured with different thicknesses of comfort padding to accommodate different ranges of head size, the required extent of protection marked on the test samples shall include the required extent of protection for each different configuration as marked on the largest head form appropriate for each.  That is:  the helmet must meet all the requirements of this Standard in each of the intended configurations.

D.  Peripheral Vision

            The clearance for peripheral vision will be checked after removing any removable peaks, bills and shades that are not essential to either the impact protection or retention systems of the helmet and that may interfere with the required clearances.  The helmet will be placed on each appropriate ISO head form, positioned according to the apposite helmet positioning index and held in place with a force of 50 newtons.  The clearances must include the following solid angles to the front of the head form:

                        1.         The upward visual clearance.

                        2.         The lateral visual clearance.

                        3.         The downward visual clearance.

             The upward visual clearance is the solid angle bounded by the reference plane of the head form and a second plane tilted 7° up from the reference plane.  This second plane intersects the reference plane at two points on the front surface of the head form that are 31 mm to the right and left of the longitudinal plane as shown in figure 3. 

Figure 3. Upward Visual Clearance


Figure 4. Lateral Visual Clearance


The lateral visual clearance, as shown in figure 4, is the solid angle bounded by the reference plane, the S4 plane and two more planes that are perpendicular to the reference plane and that contain the point on the front of the head form where the longitudinal and reference planes intersect.  One of these two planes forms an angle of 105° with the longitudinal plane and lies to the left of the head form.  The other forms the same angle to the right of the head form. 

            The downward visual clearance is the solid angle bounded by the basic plane of the head form and a second plane tilted 30° down from the basic plane that intersects it at two points on the front surface of the head form that are 31 mm to the right and left of the longitudinal plan as shown in figure 5.

Figure 5. Downward Visual Clearance


E.  Performance Testing

            The performance testing first subjects helmets to a dynamic test of retention system strength or to a test for positional stability.  The helmets are then subjected to several impact management tests.  These tests are conducted upon helmet samples either kept under laboratory ambient temperature and humidity or that have been conditioned in one of three environments simulating some of the conditions in which the helmet might reasonably be expected to be used. 

            In certification testing, the first of the five samples is kept at laboratory ambient temperature and humidity and allowed to come to equilibrium.  It is subjected to the positional stability test and then to the impact management tests.  The second, third and fourth samples are conditioned hot, cold and wet, respectively and a fifth sample is conditioned either hot, cold or wet according to the best judgement of the Foundation's technical personnel.  The second through the fifth samples are subjected to the dynamic test of the retention system and then to the impact management tests.

            In random sample testing, the sample may be at ambient temperature and humidity and subjected to either the test for positional stability or to the dynamic test of the retention system before being tested for impact management.  Otherwise, the sample may be conditioned either hot, cold or wet and subjected to the dynamic test of the retention system before being tested for impact management.

E1.  Conditioning for Testing

            a.  Cold.  The sample shall be conditioned by being exposed to a temperature of -20° C ± 2° C for a period of not less than four (4) hours, nor more than twenty-four (24) hours.

            b.  Heat.  The sample shall be conditioned by being exposed to a temperature of 50° C ± 2° C for a period of not less than four (4) hours, nor more than twenty-four (24) hours.

            c.  Wet.  The sample shall be conditioned by being continuously sprayed with water at a temperature of 25° C ± 5° C for a period of not less than four (4) hours, nor more than twenty-four (24) hours.  All of the helmets external surfaces shall be wetted continuously throughout the spray cycle.  The helmet shall not be subjected to total immersion.

             All testing of these hot, cold and wet helmets shall begin within two (2) minutes from the time of removal from the conditioning apparatus.  The samples shall be returned to the conditioning apparatus between tests.

E2.  Positional Stability (Roll-Off)

            The test for positional stability shall only be applied to samples kept at ambient laboratory temperature and humidity.  The helmet shall not have been subjected to any prior performance testing.

            The helmet shall be tested on the smallest appropriate standard full-face head form.  The head form shall be supported on a stand so that its vertical axis points downward at an angle of 135° to the direction of gravity.  The head form shall be oriented face down.  The helmet shall be placed on the head form and adjusted to obtain the best configuration of the retention system.  A wire rope shall be hooked to the edge of the helmet at the rear centerline and brought forward so that its free end hangs downward across the top of the helmet.  An inertial hammer shall be suspended from the free end of the rope.  This inertial hammer shall enable a 4.0 kg ± 50 g mass to be dropped through a 0.6 m guided fall in order to deliver an abrupt shock load to the headgear.  The shock load will force the helmet to rotate forward on the head form.  The helmet may be shifted but must remain on the head form. 

            The head form shall be repositioned so that it is facing upward but with the vertical axis still oriented downward at 135° to gravity.  The helmet shall be positioned and adjusted to obtain the best configuration of the retention system.  The wire rope/inertial hammer shall be hooked to the brow edge of the helmet at the center line so that the rope lies along the centerline and hammer is suspended from the top of the helmet.  The shock weight shall be dropped through the 0.6 m guided fall delivering an abrupt shock load forcing the helmet to rotate rearward.  The helmet may be shifted but must remain on the head form.

            The entire portion of the inertial hammer assembly that participates in the loading of the helmet shall be such that its mass is no more than 5.0 kg including the 4.0 kg shock mass.

E3.  Dynamic Test of Retention System

            The dynamic test of the retention system may be applied to any sample either kept at ambient temperature and humidity or conditioned hot, cold or wet.  However, the sample shall not have been subjected to any prior performance testing. 

            The helmet shall be placed on a head form in such a manner that the chin strap may be fastened under a device whose upper end approximates the contour of the bony structure of the jaw.  The device will then be given a mechanical pre-load followed by a dynamic loading.  The retention system fails if it cannot support the mechanical loads or if the maximum deflection during the dynamic load exceeds 30 mm.  The retention system also fails if it cannot be easily and quickly unfastened after testing. 

            a.         This chinstrap loading device shall consist of a simulated jaw and accommodations for the pre-load and dynamic load.  The jaw portion shall consist of two metal bars or rollers, each one 12.7 mm ± 0.5 mm in diameter, separated by 76 mm ± 0.5 mm on center.  The mass of this device shall not exceed 6.0 kg.

            b.         A pre-load shall be applied for at least 60 seconds. This pre-load plus the mass of the chinstrap loading device shall total 23 kg ± 500 g.

            c.         A 38 kg ± 500 g mass shall be dropped in a vertical guided fall a distance of 70 mm so as to load the retaining system abruptly; the 38 kg mass and pre-load mass shall not be additive.  In order to protect the test mechanism, the impact of the 38 kg mass may be cushioned with a 00-93 durometer rubber pad 150 mm in diameter by 6½ mm thick, or its equivalent.

E4.      Rigidity Tests

            The rigidity test is performed on a single sample kept at laboratory ambient temperature and humidity.  The sample shall be tested in a bearing press device in the following manner: the sample shall be oriented so that axis of the press element passes within 1 centimeter of the intersection of the longitudinal and S0 planes on either side of the headgear. The forces on either side of the helmet shall be applied through flat, rigid surfaces sufficiently sized and placed so that their edges extend at least 20 mm above and below the S0 plane and extend past the front and rear of the helmet.  If necessary, the helmet may be braced at its crown and brim to maintain its position in the press. 

            The press shall then be engaged to apply a force of 50 newtons and the extension of the press element shall be measured.  The element shall then be engaged to develop a force of 1000 newtons ± 50 newtons.  This force shall be maintained for no less than 120 seconds after which the extension of the press element shall be remeasured and recorded.  The difference between the two measurements shall not exceed 30 mm.

E5.  Impact Management Tests

            The impact management tests may be performed on samples kept at ambient temperature and humidity or conditioned hot, cold or wet.  Samples may be first subjected to either positional stability testing or the test for retention system strength as well as to rigidity testing.

            These tests involve a series of controlled impacts in which the helmet is positioned on a test head form.  The helmeted head form is then dropped in guided falls onto specified test anvils.  The impact site and the impact energy must meet certain requirements in order for the tests to be valid. 

            If the sample is so constructed that it interferes with the test equipment preventing impacts at sites within the test line, then, at the discretion of the Foundation's technical personnel, parts of the helmet may be cut away to facilitate testing.  Every reasonable effort to minimize such cutting will be made.  However, there shall be no relaxation of the impact levels or of the test criteria.

E5.1    Impact Management Test Equipment

            The test equipment shall consist of at least the following items:

            a.         The smallest and largest of the head forms appropriate for the helmet sample.  These head forms shall be of rigid, low resonance metal such as magnesium alloy and shall conform to the 'A', ‘C’, 'E', 'J', 'M' or ‘O’ geometries specified in ISO DIS 6220-1983.

            b.         A ball-arm/collar assembly which is fitted to a socket machined into the base of the head form.  The ball/socket configuration shall be such that the geometrical center of the ball is located on the central vertical axis of the head form 12.7 mm above the reference plane as described in ISO DIS 6220-1983.  The ball-arm/collar assembly shall also include a uniaxial accelerometer fixed firmly into the ball.

            c.         A head form support assembly rigidly attached to the ball-arm.  This support assembly shall be such that it and consequently the head form may be guided in a vertical drop.  The mass of this support assembly shall not exceed 1.2 kg.  The total mass of the head form plus ball-arm/collar assembly plus head form support assembly shall be within 100 grams of: 3.1 kg for the ISO A head form, 3.6 kg for the ISO C head form, 4.1 kg for the ISO E head form, 4.7 kg for the ISO J head form, 5.6 kg for the ISO M head form and 6.1 kg for the ISO O head form. 

d.         A guidance system such that the head form/support assembly may be guided in a vertical drop onto a test anvil.  This guidance system may consist of two or more wires or one or more rails.  The head form/support - guidance system - test anvil alignment shall be such that:

            d1.      The drop trajectory shall be a straight line within 3° of vertical and within 5° of the sensitive axis of the uniaxial accelerometer.

            d2.      The line parallel to the drop trajectory and passing through the center of the head form ball-socket shall pass within 5 mm of the center of the test anvil, within 10 mm of the center of gravity of the head form/support assembly, and within 5 mm of the sensitive element of the uniaxial accelerometer. 

            e.         A rigid anvil mount consisting of a solid mass of at least 500 kg.  The upper surface of the anvil mount shall consist of a steel plate with a minimum thickness of 12 mm and a minimum surface area of at least 0.10 m2.

            f.          Three test anvils: flat, hemispherical and horseshoe.

            f1.        The flat anvil shall have a minimum surface area of 0.0127 m2, e.g. 127 mm diameter face.  When fixed in position on the anvil mount, the surface shall be perpendicular to the head form trajectory.

            f2.        The hemispherical anvil shall have a 48 mm ± 0.5 mm radius. 

            f3.        The horseshoe anvil shall consist of a cylindrical section with its axis oriented at 45° ± 10° to present a curved striking edge.  The radius of the cylinder shall be 63.5 mm ± 0.5 mm and the radius of the striking edge shall be 1.0 mm ± 0.5 mm.  The center of this anvil shall be the highest point on the striking edge.

            g.         A uniaxial accelerometer.  The acceleration data channel must comply with SAE recommended practice J 211 requirements for channel class 1000 with the exception that the frequency response need not include the range from dc to 10 hz which may not be obtainable using certain types of transducers.

            h.         A velocity measurement device which will yield the velocity of the head form/support assembly within the last 40 mm of travel before impact.  The velocity measurements must be accurate to within ±1%. 

E5.2    Test Definitions

            a. The impact site refers to the portion of the helmet struck during an impact test.  It is defined as the point where a line passing through the center of the head form ball and the center of the anvil intersects the outer surface of the helmet at the instant the helmet first touches the anvil.

            b. The impact velocity is the velocity of the head form/support assembly as measured within no more than 4 cm of the first contact between the helmet and the impact surface.

            c.   This standard specifies nominal impact velocities which must be adjusted in order to allow for deviations between the actual mass of the test head form assembly and the specified ideal value.  The actual test impact velocity shall be the specified nominal velocity multiplied by the square root of the value obtained by dividing the ideal head form assembly mass by the actual mass.  For example, if, for the ‘A’ head form, the mass of the head form plus ball-arm/collar and support assembly as in paragraph E4.1c masses 3.2 kg instead of the ideal mass of 3.1 kg, the test impact velocities shall be obtained by multiplying the nominal velocities by a factor of 0.984.

            d. There are two levels of test: the first is the standard level used to identify those helmets which definitely meet this standard.  It is applied to samples submitted for certification testing and to those acquired for the Foundation’s random sample test (RST) program.  The second is the deviation level which is applied to samples acquired for second round RST procedures, that is: testing of samples of currently certified models for which previous samples have obtained failing results in RST testing.   Failure to meet test criteria at the deviation levels indicates that the sample definitely does not meet the requirements of the standard.

E5.3 Test Impacts

            Test impact sites shall be on or above the test line.  Rivets, vents and any other helmet feature within this region shall be valid test sites.  However, if an impact is sited closer than 120 mm to any previous impact, that later impact shall be declared invalid.

            There is no restriction regarding test anvil selection.  The impact velocities for each test impact depend on the type of test and on the head form designation.  Second impacts do not apply to helmets in tests against the edge anvil.

            The technician may select either the largest or smallest appropriate head form for any particular group of impacts.  In all cases the technician may impact any site on the helmet surface on or within the test lines as drawn for any of the head forms considered appropriate for that helmet.

             The nominal impact velocities are listed in table 4. These will be adjusted according to E5.2.c to allow for any differences between the ideal and the actual mass of the test head form assembly. If the impact velocity for any test impact exceeds the specified mass adjusted velocity by more than 1.5%, that impact shall be declared invalid.

            Please Note: The impacts described above are based on specific velocities and not prescribed drop heights.  To attain the proper velocity for an impact, it is likely that the drop height will need to be adjusted to compensate for frictions inherent in most mechanical helmet testing systems. Height adjustments for these frictions should not account for more than 10% of the total drop height.  Also, the 1.5% margin allowed for impact velocity reflects the uncertainties expected even for well-maintained drop equipment.  It is expected that drop heights will always be selected to produce, as closely as possible, the precise impact velocity as called out in the standards and adjusted for head form assembly drop mass. Each sample will be subjected to no more than four test impacts.  Test impact sites shall be on or above the test line with no allowance for the cut of the helmet no matter how closely the edge of the helmet encroaches on this test line.  However, if a test impact is sited closer than 120 mm to any previous test impact site on that sample, that impact shall be declared invalid.

Table 4. Nominal Impact Velocity Table (m/sec)

Test Type


Head Form






















Horse Shoe






















Horse Shoe








E5.4    Impact Test Interpretation

Table 5. Peak Acceleration Criteria

Head Form







275 G

275 G

275 G

275 G

264 G

243 G


            The peak acceleration of the head form shall not exceed the values in the table above depending on the head form.  The helmet’s protective structures shall not break apart throughout the testing.  If the Foundation's technical personnel conclude that fracture of the helmet shell, impact liner, retention system or other components could reasonably imply an undue laceration hazard either from the impact surface or from the helmet itself, the sample shall be considered to have failed. 

            If, in certification testing, a sample is found to meet all the test criteria but any two of the impacts were at less than 97% of the specified impact velocity as adjusted for drop assembly mass, the testing for that sample shall be declared inconclusive and must be repeated.  Finally, if an invalid impact produces a peak acceleration exceeding the test criterion, the testing for the sample shall be declared inconclusive and must be repeated.

            The impact test procedures leave considerable latitude to the helmet tester regarding site and anvil selection.  It is expected that the tester will orchestrate each standard test series in order to investigate potential weaknesses and to exercise each likely failure mode and will conduct deviation level testing to exercise the failure modes identified previously.

            If at the end of a certification test series, the Foundation's technical personnel conclude that the results obtained in valid impacts are not sufficient to determine whether the helmet model meets the performance requirements of this standard, additional samples may be conditioned and tested.  It is expected that all samples submitted will meet all the test requirements.

E6.      Shell Penetration Test

                        The shell penetration test may be applied to helmets kept at laboratory ambient temperature and humidity or helmets conditioned hot, cold or wet. At least one helmet sample shall be tested in shell penetration.  The complete helmet shall be placed on a rigidly mounted head form.  The test head form for the penetration test need not be the standard ISO head form shape used in the impact testing and helmet marking.  It is expected only that the device used will provide reasonable support for the helmet and conformance with the interior of the helmet immediately beneath the site of the penetration test.  If the helmet contains a sling or some other adjustable sizing component, it shall be relaxed to its most extendable position.

            The penetration test striker shall have a mass of 3 kg ±50 g and the point of the striker shall be a cone with an included angle of 60º ±0.5º and an altitude of 38 ±0.38 mm.  The striking tip shall have a hardness of 60 Rockwell (scale C ± 3 points) and a radius of 0.5 ± 0.1 mm.  The region of the support head form directly beneath the striker tip shall be wax or soft plastic so and covered with a thin tell-tale of paper, foil, tape or some similar material.

            The striker shall be dropped to strike the surface of the helmet shell at a velocity of 4.30 ± 0.15 meters per second as measured when the striker is no more than 4 centimeters away from contact with the helmet. The helmet may be oriented on the support head form so that the test striker is directed at any site on or above the test line but the penetration test site must be at least 7.5 cm removed from the center of any impact test site or any other penetration test site.  At the test technician’s discretion, samples may be tested at more than one site on the shell.

            For all penetration tests performed, the test striker must not penetrate through the helmet wall so as to put a hole in the tell-tale between the helmet and the support head form.

Certification Series Test Plan

            For a certification test series, it is expected that each test in this standard appropriate to the helmet configuration will be performed at least once.  It is also expected that the test technician will conduct the testing so as to obtain the most exhaustive evaluation possible of likely failure modes.  The table below represents a typical certification test plan by sample number, conditioning and tests in order of application.  Bolding indicates that the particular test is routine for that sample; otherwise, the particular test might be performed on another sample if convenient. Italics indicate the test is optional for that sample at the discretion of the technician.  Aside from comfort padding, all samples must be identical. The first six samples are to be equipped with comfort padding appropriate to the largest intended head circumference and will be tested on the largest appropriate head form. Samples #7 and #8 are necessary only when the smallest appropriate head form is not the same as the largest appropriate.

            The E4 Rigidity Test might conceivably be performed on any sample in the set but only if the sample has been maintained at laboratory ambient temperature and humidity for at least four hours immediately before the Rigidity Test procedures are applied. 

Test Matrix



Appropriate Tests

#1 Archive


Marking and Visual Field Only


Lab Ambient

E2, E4, E5, E6



E3, E5, E6



E3, E5, E6



E3, E5, E6


Lab Ambient or Hot

E3, E4 (ambient only), E5, E6



Visual Field, E2, E5



E3, E5


                 [1]The Foundation has also published Standards for headgear used in bicycling, non-motorized sports, motorcycling, automobile racing, Karting, skiing and snowboarding and in equestrian (harness racing) activities.  Copies of these Standards are available on request.