FR Apparel Newsletter Volume 7

New AGA Fire Study Offers Key Learnings for Fire Hazards in Your Industry

The American Gas Association (AGA) is a trade organization representing more than 200 companies that service 95% of natural gas customers in the United States. The AGA recently completed an extensive study of workplace natural gas fires, providing new data that safety managers can use in their heat/flame hazard assessments. The key learnings from this study can be applied to other industry work environments where a thermal hazard exists.

The AGA study was supported by 14 natural gas and safety companies and included fire science experts from DuPont. The study focused on four main questions:

  1. What is the escape time for a worker in different work environments wearing different types of personal protective equipment (PPE)?
  2. How long does it take a standby employee to extinguish an excavation fire?
  3. How much heat is generated by a natural gas fire and what is the maximum exposure temperature?
  4. What is the relative performance of different flame-resistant (FR) garment configurations at extended exposure times?

This article presents some key findings for each of these four questions.

Escape Time

In this study, a worker simulating an excavation job assignment began by either standing or kneeling on one knee at a pipe buried to a depth of either 4 or 6 feet. Escape time was measured from the starting location to a point 10 feet away.

Worker Simulating Escape Time

  • The average escape time across all conditions was 3.85 seconds and did not include normal human reaction time to perceive danger and react, which could add an additional 1.5 seconds.
  • Escape times varied by up to 45% based on the age, gender, body size and years of service of the employee.
  • Escape time was not affected by the weight or type of FR garments worn, but was negatively affected by restricted vision from a respirator.
  • Escape time was longer from workplace environments that included a ladder, but under duress not all participants used the ladder to escape.

Bystander Firefighting

A bystander employee at a starting location 10 feet from an excavation fire (at depths of either 4 or 6 feet) was timed until the fire was put out. Study participants used a common dry powder extinguisher.

Bystander firefighting

  • The average time to extinguish the fire was approximately 6 seconds.
  • Fire extinguisher weight or powder type did not affect extinguishing time, but multiple strikes to puncture a new cartridge could add as much as an additional 10 seconds to put out the fire.

Heat Flux

For this study, a first-of-its-kind system using slow-motion infrared video imagery was designed to measure the fire intensity that would occur in the locations of a worker or standby employee involved in a natural gas excavation fire.

Temperature and Heat Flux Data

  • The average heat flux was approximately 2 calories / (cm2·s), with the highest heat intensity observed 3 feet from the floor of the excavation.
  • The maximum temperature of exposure was on average 200°C (392°F).

PPE Protection Levels

Outcomes of these three studies were used to compare the predicted body burn of different FR PPE multi-layer garment systems. Thermal manikin testing was conducted at a heat flux of 2 calories / (cm2·s) using the testing procedures in ASTM F1930 at exposure times of 4, 6 and 8 seconds. For the results shown in the figure below, the thermal manikin was dressed in cotton undergarments, cotton jeans and an FR coverall constructed of either Nomex® IIIA, FR-treated cotton or modacrylic blend, as noted. Total predicted burn injury (TPBI) results do not include the head.

TPBI Data

  • Garments made of Nomex® IIIA generated lower predicted body burn at lower fabric weights for all exposure times compared with modacrylic blends or FR-treated cotton.
  • Garment weight alone is not a reliable predictor of FR garment protection.
  • Proper sizing and fit of FR garments is very important for protection. Wearing garments that are too tight can increase predicted burn injury by up to 15%.

Conclusion

Although this study was conducted for the natural gas industry, the findings may be transferred to other work environments where a thermal or fire hazard exists.

To help you make the most of this new data, Caroline Holtzman, DuPont™ Nomex® FR Technical Leader, presented a webinar on September 26, 2018, to explain how the findings from the extensive AGA fire study can be applied to workplaces outside the natural gas industry. Don't worry if you missed the live event because it is now available for viewing.

Download the final report from AGA which contains a comprehensive review of the study facts, figures and conclusions—and also view the accompanying video on the Nomex® Knowledge Center.



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