Advances in Protective Clothing

Advances in Protective Clothing

Flame tests of fire fighting clothing are conducted at Natick, Mass., Army Development Center by pulling instrumented manikins through fire at a prescribed rate. Readings obtained indicate protective qualities of garments and materials.

Fire fighting is one of the nation’s most dangerous occupations, but the odds of being injured can be significantly reduced by the selection of proper protective clothing. Not only the type of clothing, but also knowledge of the usage limitations of the clothing is important.

When you come right down to action on the fireground, the fire fighter is the one most responsible for protecting himself. Consequently, the best body protection is of little or no value if the fire fighter does not understand his clothing’s limitations.

Before examining clothing in detail, let’s look quickly at fires and fire fighting techniques that have changed the fire fighter’s exposure to potential hazards.

Modern hazards

There are new aspects to fires today that were not as prominent or even in existence 50 or 75 years ago. For example, gasoline – once an exotic chemical – is now a household item and a more frequent ingredient in today’s fires. Chemicals, petrochemicals and jet-age fuels – once found only in test tubes – are now produced, stored and shipped in vast quantities, adding a new dimension to industrial fire fighting.

To fight these fires, techniques and equipment have had to be developed and upgraded and these advances have brought the fire fighter closer to the fire. Advances such as improved aerial equipment, radio equipment, high pressure pumps, fogs, foams and Halon 1301 and CO2 gases, and selfcontained breathing apparatus are commonplace with fire companies. But as the fire fighter has been brought closer to the fire, his exposure has increased sharply.

Protective clothing

Along with advances in equipment have come improvements in protective apparel in terms of both materials and design. Different types of garments now are available specifically for various hazard levels. Proximity and entry suits are good examples of gear to be used in extreme hazard situations.

The average municipal or volunteer fire fighter also has available greatly improved protective clothing. However, the fire fighter has not had the benefit of a standard to guide him in the selection and proper wear and care of protective garments for more normal situations. A step in this direction is being taken by organizations such as the National Fire Protection Association, the National Fire Prevention and Control Administration, the International Association of Fire Fighters and the International Association of Fire Chiefs.

Proposals for standard

The NFPA, as an example, is developing a standard for some basic items of protective clothing, such as turnout coats and pants which would offer protection in conventional fire situations faced by fire fighters. The proposed standard calls for:

  • A three-layer system – shell, vapor barrier and lining. The NFPA has set minimum protection requirements which call for all three layers to be used at all times.
  • All materials must be flame retardant and heat stable up to 500° F. This is to keep the garment from contributing to or injuring the fire fighter once he has been exposed.
  • Lightweight: maximum coat weight 7 pounds, (size 40); maximum pants weight 5 pounds (size 36, 32-inch inseam).
  • The shell fabrics should be tough and durable to withstand abrasion, high temperature exposure, chemical attack (such as battery acid), mildew rot; have low moisture pickup; be flexible at all temperatures and permanently flame retardant.
  • The vapor barrier should keep water and corrosive liquids from passing through, but more importantly should stop hot gases or steam from getting to the body. (Steam burns or scalds can happen when the wet shell fabric comes in contact with open flame or hot embers. The water flashes to steam and unless a vapor barrier stops it, the steam comes in contact with the skin). The vapor barrier must be flame retardant.
  • The lining’s function is to insulate against conductive heat. (This is so important that the liner must be used in summer as well as winter.)
  • An additional liner may be used in winter and removed during the summer. This winter liner, as such, is not considered a basic part of the coat.

Fire fighters are called upon to wear turnout gear every day and they should expect their gear to perform well under the proposed NFPA requirements.

Tests devised

However, the degree to which turnout gear fabrics meet the NFPA standard needed more documentation. In answer to this need and as a result of years of government agencies such as the Natick Army Development Center, tests have been devised to approximate realistic conditions and yield data that will define protection. The Du Pont Company has now developed laboratory test procedures and data on the level of physical and protective qualities of typical fabrics used in turnout clothing.

It is the very nature of a fire fighter’s job that requires protective clothing. It may include extended exposures to radiant energy from a bright yellow flame of 1500° to 2000°F, which can cause the surface of the turnout coat to be heated to temperatures up to 500°F or higher – a temperature level which can cause permanent damage to some fabrics and burn the skin.

On the other hand, exposure may occur by direct contact with flames for a matter of seconds. Short, intense exposure of this nature may take the form of flashovers or solvent fire eruptions and require turnout coat materials that offer high temperature resistance and good heat protection.

Coat systems tested

To determine the performance of typical turnout coat systems to give thermal protection from a theoretical second degree burn – a criterion used by the military as the failure point of a garment – a test was devised to expose fabrics to a 2.0 cal./cm2/sec. 50/50 radiant convective heat load similar to what you may expect in a fully involved structural fire. The accompanying chart presents findings for a number of typical systems in use.

These data indicate each turnout coat system’s ability to isolate and insulate the wearer from a high thermal hazard. The systems with the combination of the highest ratings, (longest period of resistance to the thermal test exposure)and lowest weight are optimum for the variety of thermal hazards a fire fighter experiences.

Thermal Protective Performance (TPP) Ratings Of Typical Turnout Coat Systems*

The Optimum System Is A High TPP Rating

Combined With Low Weight

*A System theoretically consists of a Shell Fabric(S)Vapor Barrier(V) and a Thermal Lining(L) A Single fabric may sarva as two or mora of these layers as indicated.

**FRT is an abbreviation for Fire Retardant Treated

The importance of the combination of material, weight and thickness is demonstrated in the table.

Weight and protection

For example, note that the system comprised of the vinyl-coated fabric and wool lining is thicker and heavier than the three-layer system of 7.5ounce duck of Nomex aramid, neoprene coated fabric of Nomex, and quilted Nomex. However, the Nomex system offers nearly 30 percent more protection than the fire retardant treated cotton duck – neoprene-coated cotton flannel.

The additional weight of a wet coat is a negative feature. Coats, however, are exposed to water from accidental or purposeful wetting. The normal weight of the fire fighters’ gear makes it advantageous to choose a coat that will absorb the least amount of water. To determine the amount of absorption, fabrics were weighed after soaking them in water for 60 minutes.

Comparison of Weight, Thickness, and Thermal Protective Performance (TPP) of Typical Turnout Coats

*A System theoretically consists of a Shell Fabric(S),Vapor Barrier*and a Thermal Lining*1-). A Single fabric may serve as two or more of these layers as indicated.

**FRT is an abbreviation for Fire Retardant Treated.

Note that coated polyester and Nomex absorbed the least amount of water while the cotton duck more than doubled its weight. By the same token, fabrics which absorb less water dry more quickly.

Facts about clothing

The NFPA standard and the findings from Du Pont on protective qualities point to a number of facts that every fire fighter should remember about his turnout clothing:

  • All protective clothing has a failure point. The objective is to move the failure point as far out in time as possible and yet, remain within the other practical and economical requirements of today’s fire fighter. Turnout gear is not an entry suit; don’t expect it to perform as such. Entry suits are designed differently. Your turnout gear is designed to allow you to fight fire at a safe distance and to protect you against unexpected exposures as much as possible.
  • Wear turnout pants of the same construction as your coat or at least wear a station uniform or coveralls of a high temperature resistant, inherently fire retardant fabric which can give you more protection than street or regular work clothes.
  • Wear your protective clothing as it is designed to be worn all the time you are fighting the fire. That means with the lining in, collar up, boots up and coat closed. You might get uncomfortable, but it can mean the difference between going home and being able to fight fires another day or going to the hospital.
  • Keep your gear clean. Soiled or dirty clothing can lead to contaminated fabric which is no longer flame retardant. Keep it clean for maximum protection and keep it dry and in good repair.

The NFPA standard offers a giant step foward in establishing qualifications for fire fighter’s turnout clothing. Turnout clothing that meets the standard will meet an indentifiable protection level – a vital benefit for the fire fighter. In addition, with the data such as that developed by Du Pont, the fire fighter will be able to rate the degree of thermal protection that he can expect to receive.

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