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What is a Flash Fire?
“A flash fire is spread rapidly through a diffuse fuel, such as dust, gas, or the vapors of an ignitable liquid, without production of damaging pressure.” Flash fires are typically three seconds or less, but are fast-moving and intense. The severity is contingent on environmental factors such as the fuel available and the efficiency of combustion.
OSHA CFR 1910.132 states that “Protective equipment…shall be provided, used, and maintained in a sanitary and reliable condition wherever it is necessary by reason of hazards of processes or environment, chemical hazards, radiological hazards, or mechanical irritants encountered in a manner capable of causing injury or impairment in the function of any part of the body through absorption, inhalation or physical contact.” This regulation holds the employer responsible for providing PPE whenever such PPE can protect the employee from a known hazard: environmental, chemical, or mechanical. This standard applies to hazards beyond those posed by arc flash, a hazard faced by electric workers.
OSHA CFR 1910.132 has typically been applied to workers in the chemical industries but has recently been interpreted by OSHA to include the flash fire hazards in the well drilling, servicing, and production-related industries. OSHA specifies that FR clothing should be used in these industries in a letter of interpretation. “The use of FRC greatly improves the chance of a worker surviving and regaining quality of life after a flash fire. FRC can significantly reduce both the extent and severity of burn injuries to the body.” Though the regulation itself does not address FR clothing, OSHA’s interpretation (dated March 19, 2010) of the regulation DOES require FR clothing for the above industries.
Compliance with OSHA 1910.132 requires the use of FR clothing in the well drilling, servicing, and production-related industries if a flash fire hazard exists. OSHA’s General Duty Clause also requires the employers to protect workers by any reasonable means from known workplace hazards, such as flash fire. For other industries, the employer is required to provide as much personal protective equipment as needed to protect against environmental hazards, chemical hazards, radiological hazards, or mechanical irritants. FR clothing helps to protect the wearer against flash fire in these industries as well.
There are two standards; both were developed by the National Fire Protection Association (NFPA). They are: NFPA 2112 Standard on Flame Resistant Garments for Protection of Industrial Personnel Against Flash Fire (2007 Edition) and NFPA 2113 Standard on Selection, Care, Use and Maintenance of Flame-Resistant Garment for Protection of Industrial Personnel Against Flash Fire (2007 Edition). Together, they offer guidance to industry leaders on helping to protect workers against the hazards of flash fire.
Developed specifically to address flash fire hazards, the intent of NFPA 2112 is “not contributing to the burn injury of the wearer, providing a degree of protection to the wearer, and reducing the severity of burn injuries resulting from accidental exposure to hydrocarbon flash fires.” It provides guidance on minimum performance standards and test methods for garments used to protect workers against flash fire hazards including flame resistance, heat and thermal shrinkage resistance and thermal protective performance (TPP).
The manikin test, ASTM 1930, Test Method for Evaluation of Flame Resistant Clothing for Protection Against Flash Fire Simulations Using an Instrumented Manikin, is a commonly cited test method in NFPA 2112 (one of many). Fabrics are tested using the standard garment design a men’s coverall described in F1930. It uses an exposure heat flux of 84 kW/m2 (2.0 cal/cm2.sec) with an exposure time of three seconds. The average predicted body burn rating is calculated and reported in the fabric test results. If the tested garment delivers less than 50 percent total body burn rating, the fabric achieves a passing performance. For flash fire manikin test results of Tyndale’s M110T, click here.
The results of TPP, as specified by NFPA 2112, are based upon the response of the sensors versus exposure time, rounded to the nearest 0.1 second. This result is the amount of heat and time needed to create a second-degree burn. The TPP rating for each test is calculated as the product of exposure energy heat and time, using the following equation:
· TPP rating=(F)(t)
The 2007 edition of 2112 requires the TPP test to be performed both with the fabric sample in contact with the sensor and with the fabric sample separated from the sensor with a 1/4” spacer. A minimum TPP rating of 6.0” for “spaced” and 3.0” for “contact” is required to meet the standard. Pass or fail is based upon the average TPP ratings for both “spaced” and “contact” tests. NFPA 2112 Table B.1 (an appendix table) offers a comprehensive summary of test properties and methods. Not all tests listed in the table are required under NFPA 2112, but the information is very useful.
NFPA 2113 2007 edition offers guidance on the selection, care and use of flame resistant garments. New language added to the standard in the 2007 edition includes details on the selection criteria for flame resistant garments. Also, 2113 also now includes a recommendation that flame resistant or non-melting undergarments shall be used; this recommendation is considered a “best practice” in the industry.