Flammability, Smoke Emission  & Toxicity

The following excerpt is a generic set of flammability criteria intended for passenger transit rail vehicle specifications. The requirements are based on a combined set of criteria from NFPA 130 - 2014, the current 49 CFR 238.103, and Appendix B to Part 238, and industry informal standards such as Boeing BSS-7239, and Bombardier Transportation SMP 800-C.


All materials used in the vehicle shall comply with the flammability; smoke emission, toxic gas, and fire retardation requirements specified herein.

Materials used in the construction of the vehicle shall meet the requirements contained in this section, 49 CFR 238.103, Appendix B to Part 238, and NFPA 130 - 2014.

Should a conflict exist between the NFPA and Federal requirements and requirements listed elsewhere in these provisions, the more restrictive shall govern. Note: the FRP smoke requirement has been modified to a more restrictive value to improve smoke characteristics for tunnel operation.

Materials used in the construction of the vehicle shall be selected to minimize the total combustible material content of the vehicle.

The Contractor shall furnish a comprehensive listing of materials used in the vehicles in matrix form (flammability matrix). The flammability matrix shall include the following information as a minimum:
  • Material application (component description, part/drawing number, and location)
  • Material supplier (full name of material manufacturer)
  • Material description (actual material name and trade name)
  • Material part number, formula number, or compound number
  • Material weight (both density and total weight in vehicle)
  • Flammability data as applicable:
    • Flame spread / flammability
    • Smoke generation
    • Heat value per pound
    • Heat release rate
    • Total heat released
    • Flashpoint / autoignition temperature
    • Toxic content in combustion products
  • Testing laboratory (full name of independent testing entity)
  • Submittal letter (letter number(s) submitting test reports and material specifications)
  • Response Letter (letter(s) dispositioning the latest submission of data)
  • Approval status (current approval status of the specific material)
The Contractor shall submit laboratory test results for all materials, for all tests specified, including a technical data sheet, for approval. The flammability matrix shall contain sufficient information to positively identify each material listed [CDRL Requirement].

The material description used by the contractor shall be identical in every place it appears; test report documentation, technical data sheet, drawings, bill of materials, flammability matrix, and other related references. This documentation must be directly traceable between the technical documentation, test reports and flammability matrix, to the applicable Contractor drawings without ambiguity.

Copies of prior test results showing that proposed materials have complied with the specified standards and tests may be submitted for approval if the test reports are no more than three years old. Assurance may be required that the material presently being considered for use is the same composition as that previously tested.

Flammability And Smoke Generation Criteria

Function of Material
(see comments)
Test Procedure Performance Criteria

All vehicle materials & components except as otherwise noted. 
(Wall Panels, Ceiling Panels, Partition Panels, Windscreens, Fiberglass, Plastics, Diaphragms, Non-sealing Elastomers, etc.) (1, 2, 9, 12)

ASTM E 162
ASTM E 662

Is ≤ 35
Ds (1.5) ≤ 100, Ds (4.0) ≤ 200
(to exclude polyester resin FRP, use the following: Ds (1.5) ≤ 100, Ds (4.0) ≤ 165)

HVAC Ducting
(1, 2)

ASTM E 162
ASTM E 662

Is ≤ 25
Ds (4.0) ≤ 100

Lighting Diffusers / Plastic Glazing
(2, 14)

ASTM E 162
ASTM E 662

Is ≤ 100
Ds (1.5) ≤ 100, Ds (4.0) ≤ 200

Thermal and Acoustical Insulation
(1, 2)

ASTM E 162
ASTM E 662

Is ≤ 25
Ds (4.0) ≤ 100

Flexible Cellular Foams
(1, 2, 4, 6)

ASTM D 3675
ASTM E 662

Is ≤ 25
Ds (1.5) ≤ 100, Ds (4.0) ≤ 175

Elastomers – Lock strip gaskets
(1, 2, 10, 11)

ASTM C 542
ASTM E 662

Pass criteria in table 1
Ds (1.5) ≤ 100, Ds (4.0) ≤ 200

Elastomers – Other gaskets or seals
(1, 2, 10, 11)

ASTM C 1166

ASTM E 662

100mm (4.0in), maximum flame propagation (15)
Ds (1.5) ≤ 100, Ds (4.0) ≤ 200

Adhesives and Sealants

ASTM E 162
ASTM E 662

Is ≤ 35
Ds (1.5) ≤ 200, Ds (4.0) ≤ 200

Structural – Floor, Roof
(16, 17, 18)

ASTM E 119

Pass (30 Minutes minimum endurance at AW3 loading)

Floor Covering
(12, 13)

ASTM E 648
ASTM E 662

CRF > 0.5 W/cm2 (5kW/m2)
Ds (1.5) ≤ 100, Ds (4.0) ≤ 200

Seat Cushions, Mattresses
(1, 2, 3, 4, 5, 6, 7, 8)

ASTM D 3675
ASTM E 662

Is ≤ 25
Ds (1.5) ≤ 100, Ds (4.0) ≤ 175

Seat Frame, Seat Shroud
(1, 2)

ASTM E 162
ASTM E 662

Is ≤ 35
Ds (1.5) ≤ 100, Ds (4.0) ≤ 200

Upholstery
(1, 2, 3, 6, 7, 8)

14 CFR (FAR) 25.853 (Appendix F, vertical, textiles)
ASTM E 662

Flame Time ≤ 10 sec.
Burn Length ≤ 150 mm, (6").
Ds (4.0) ≤ 200

Wire Insulation
(1, 2, 19)

NFPA 130 - 2014

Requirements for Wiring and Electrical Insulation.

Note: The previous requirement for wiring flammability was per IEEE Std 383 - Flammability. The 2014 NFPA 130 criteria cites a number of sources for wiring flame and smoke performance too numerous to repeat the list here.

Note: More History: The smoke density for the wiring was listed as ASTM Ds (4.0) ≤ 50. This is much less than previous values of ASTM Ds (4.0) ≤ 75(NF) and ASTM Ds (4.0) ≤ 200 (F) used on other prior projects. The overall trend is a general reduction in smoke generation.

Numbered comments are based upon NFPA 130, and 49 CFR Appendix B to Part 238.  These comments have been either quoted, combined from both, or adapted/edited to passenger transit applications.

1) Materials tested for surface flammability shall not exhibit any flaming running or dripping unless an appropriate fire hazard analysis is conducted and approved by the Transit Authority.

2) The ASTM E 662 maximum test limits for smoke emission (specific optical density, Ds) shall be measured in both the flaming or non-flaming mode, values shall be provided for both cases. The maximum smoke density, Dm, shall also be provided for information.

3) Testing of a complete seat assembly (including cushions, fabric layers, upholstery) according to ASTM E 1537 using the pass/fail criteria of California Technical Bulletin 133, and testing of a complete mattress assembly (including foam and ticking) according to ASTM E 1590 using the pass/fail criteria of California Technical Bulletin 129 shall be permitted in lieu of the test methods prescribed herein, provided the assembly component units remain unchanged or new (replacement) assembly components possess equivalent fire performance properties to the original components tested. Testing shall be at 50 kW/m2 applied heat flux with a retainer frame. A fire hazard analysis must also be conducted that considers the operating environment within which the seat or mattress assembly will be used in relation to the risk of vandalism, puncture, cutting, or other acts which may expose the individual components of the assemblies to an ignition source. The requirements of Notes 5, 6, 7, and 8 shall be met.

4) Testing is performed without upholstery.

5) The surface flammability and smoke emission characteristics shall be demonstrated to be permanent after dynamic testing according to ASTM D 3574, Test I2 (Dynamic Fatigue Test by the Roller Shear at Constant Force) or Test I3 (Dynamic Fatigue Test by Constant Force Pounding) both using Procedure B, except that the test samples shall be a minimum of 6 inches (154 mm) by 18 inches (457 mm) by the thickness of the material in its end use configuration, or multiples thereof. If Test I3 is used, the size of the indentor described in paragraph 96.2 shall be modified to accommodate the specified test specimen.

6) TThe surface flammability and smoke emission characteristics shall be demonstrated to be permanent by washing, if appropriate, in accordance with the manufacturer's recommended procedure. If a washing procedure is not provided by the manufacturer, the fabric shall be washed in accordance with ASTM E 2061, Annex A1.

7) The surface flammability and smoke emission characteristics shall be demonstrated to be permanent by dry-cleaning, if appropriate, according to ASTM D 2724.

8)  Materials that cannot be washed or dry-cleaned shall be so labeled and shall meet the applicable performance criteria after being cleaned as recommended by the manufacturer.

9) As a minimum, all combustible materials used anywhere in the vehicle (except as noted in 10) are required to be tested including interior, cab components as well as exterior components. Combustible signage shall not be required to meet flame spread or smoke emission requirements if (a) the actual thickness of the signage is no greater than 1.5 mm (0.060 in.); (b) the aggregate area of combustible signage does not exceed 10 percent of the wall area of the car, including windows; and (c) no single sign is larger than 0.47 m2 (5.0 ft2). Items that cannot be made compliant due to other dominating engineering requirements may not be required to meet the flammability or smoke emission performance criteria specified, but still must be tested to establish the relative risk and evaluated, and waived, by the Transit Authority.

10) Materials used to fabricate miscellaneous, discontinuous small parts (such as knobs, rollers, fasteners, clips, grommets, and small electrical parts) that will not contribute materially to fire growth in end use configuration are exempt from flammability and smoke emission performance requirements, provided that the surface area of any individual small part is less than 16 square inches (100 cm2) in end use configuration and an appropriate fire hazard analysis is conducted which addresses the location and quantity of the materials used, and the vulnerability of the materials to ignition and contribution to flame spread.

11) If the surface area of any individual small part is less than 16 square inches (100 cm2) in end use configuration, materials used to fabricate such a part may be tested in accordance with ASTM E 1354 as an alternative to both (a) the ASTM E 162 flammability test procedure, or the appropriate flammability test procedure otherwise specified in the table, and (b) the ASTM E 662 smoke generation test procedure. Testing shall be at 50 kW/m2 applied heat flux with a retainer frame. Materials tested in accordance with ASTM E 1354 shall meet the following performance criteria: average heat release rate (q̇''180) less than or equal to 100 kW/m2, and average specific extinction area (sf) less than or equal to 500 m2/kg over the same 180-second period.

12) Carpeting used as a wall or ceiling covering shall be tested according to ASTM E 162 and ASTM E 662 and meet the respective criteria of Is less than or equal to 35 and Ds (1.5) less than or equal to 100 and Ds (4.0) less than or equal to 200. Notes 1 and 2 apply.

13) Floor covering shall be tested with padding in accordance with ASTM E 648, if the padding is used in the actual installation.

14) For double window glazing, only the interior glazing is required to meet the requirements specified herein. (The exterior glazing is not required to meet these requirements.)

15) Average flame propagation shall be less than 4 inches and no specimen shall be completely consumed.

16) Penetrations (ducts, access openings, etc.) shall be designed against acting as passageways for fire and smoke and representative penetrations shall be included as part of test assemblies.

17) A structural flooring assembly separating the interior of a vehicle from its undercarriage shall meet the performance criteria during a nominal test period as determined by the railroad. The nominal test period must be twice the maximum expected time period under normal circumstances for a vehicle to stop completely and safely from its maximum operating speed, plus the time necessary to evacuate all the vehicle's occupants to a safe area. The nominal test period must not be less than 30 minutes. Only one specimen need be tested. A proportional reduction may be made in the dimensions of the specimen provided it serves to truly test the ability of the structural flooring assembly to perform as a barrier against under-vehicle fires. The fire resistance period required shall be consistent with the safe evacuation of a full load of passengers from the vehicle under worst-case conditions.

18) Portions of the vehicle body which separate major ignition sources, energy sources, or sources of fuel-load from vehicle interiors, shall have sufficient fire endurance as determined by a fire hazard analysis acceptable to the railroad which addresses the location and quantity of the materials used, as well as vulnerability of the materials to ignition, flame spread, and smoke generation. These portions include equipment carrying portions of a vehicle's roof and the interior structure separating the levels of a bi-level car, but do not include a flooring assembly subject to Note 17.

19) Testing shall be conducted in accordance with ANSI/IEEE Standard 1202, with the additional requirement that circuit integrity shall continue for 5 minutes after the start of the test. 

20) Testing of cured materials shall be conducted on materials that are completely cured as stated by the manufacturer's specifications.

Toxic Content Limits In Combustion Products

The maximum toxic gas concentration in the combustion products of any materials used in the construction of the vehicle shall not exceed the following values:


Toxic Gas – Boeing BSS-7239
(or Bombardier SMP 800-C)
Maximum Concentration
Carbon Monoxide  (CO), 3500 ppm
Hydrogen Fluoride  (HF), 200 ppm
Nitrogen Dioxide  (NO2), 100 ppm
Hydrogen Chloride  (HCL), 500 ppm
Hydrogen Cyanide  (HCN), 150ppm
Sulfur Dioxide  (SO2), 100 ppm