PPE201

Relevant Standard(s)

NFPA 1971: Standard on Protective Ensembles for Structural Fire Fighting and Proximity Fire Fighting(Mandatory in Ontario).

Key Terms Relating to Material Composites

CCHR: Conductive and Compressive Heat Resistance - measures the level of thermal protection in key areas of the bunker suit which are typically subjected to compression (i.e. shoulders & knees)The test represents time for a temperature rise (24*C) when a source of heat(280*C) and pressure is applied.

NFPA 1971 standard requires a minimum CCHR of 25 seconds.

THL: Total Heat Loss - measures the heat stress reduction capability (or breathability)The more heat that gets trapped inside a firefighter's bunker gear, the more likely an individual may experience dangerously elevated skin and core temperatures, as well as an increased heart rate. Material systems that provide a higher THL will benefit the f irefighter in the form of more breathable turnout gear.

The NFPA 1971 standard requires a minimum THL of 205W/m2.

TPP: Thermal Protective Performance - indicates the level of protection against both convective and radiant heat. To determine actual time to burn, the TPP is divided in half and the resulting number is the time (in seconds) that human tissue reaches second degree burn in a flash over situation.

The NFPA 1971 standard requires a minimum TPP rating of 35.

Moisture Barrier Criteria

While the moisture barrier has a number of supplemental functions, its main job is to keep the thermal protective properties of the system intact by preventing external water from penetrating into the critical air spaces of the garment.A dry system is safer, more dependable, and a lot lighter in weight than a wet one. All moisture barriers will shed external water, but there are significant differences in their durability, thermal integrity, and long-term reliability.Another important aspect of moisture barrier protection is the ability to “breathe”. A more breathable barrier will usually reduce the amount of moisture and body heat that can be trapped inside the gear. Highly-breathable moisture barriers are intended to prevent water from entering into the thermal layers, while allowing body vapour from sweat to escape outward. Additionally, moisture barriers with high thermal integrity, or those well protected by other layers, are less likely to break open during “flash-over” conditions.

Moisture Barrier Offerings

An ever-increasing number of barrier films are used throughout the world. Many are available for use in NFPA 1971 gear. The differences between one urethane-type polymer barrier and another are relatively insignificant. The differences are even less meaningful when compared to the clear-cut advantages of Gore’s bicomponent moisture barriers. It’s recommended to specify a world-class product, such as a CROSSTECH® moisture barrier laminated to a rugged Nomex® woven pajama check, or the thermally-stable, cost-competitive PTFE-based Gore RT7100™ moisture barrier laminated to a non-woven.GORE RT7100™ Moisture Barrier meets the performance needs and cost considerations of specific markets. A durable, breathable alternative to less expensive barriers and textiles, it provides a reliable combination of thermal stability and liquid penetration resistance unmatched in its price range.CROSSTECH® Moisture Barrier provides the best Total Heat Loss (THL) in today’s market, while offering outstanding durability. The thin flexible barrier delivers greater overall performance.CROSSTECH® 3-Layer Moisture Barrier is the most durable, flexible and abrasion-resistant moisture barrier available. It provides the best combination of durability, THL and TPP in a rugged three-layer construction for the most demanding scenarios.

The thermal liner is arguably the most significant layer of protective material within a bunker suit and its selection deserves thorough consideration.

Air Layers and Thermal Liners

The protective value of the fabric composite is really found in the air that’s between the fire fighter and the heat source. Air itself is the greatest single source of the insulative qualities in protective clothing. Best of all, it weighs nothing and it’s free! The most functional way to achieve the best protection is to use a multi-layer configuration in which each layer accomplishes part of the job. Extremely efficient insulation can be gained by creating very thin air spaces between the layers, which supplement the air contained within the layers. It’s important that none of these individual air spaces exceed 1.8 cm of thickness, because convective currents start beyond that thickness and may begin to quickly transmit heat. Similarly, air layers that are replaced by water can be unpredictably dangerous. Unlike air, water is an amazing conductor of heat.It is logical that the thermal barrier systems which have the most air spaces can create the most layers of air or can resist absorption (water replacement of the insulating air) will provide the most reliable protection.Another important consideration for thermal barriers relates to comfort and mobility. It is now widely recognized that thermal barriers which use slippery yarns on the “face cloth” next to the wearer are far less likely to bind and restrict the fire fighter’s movement. The super-strong filament yarns which create this lubricity are also excellent at wicking perspiration away from the body.

Batting, Non-Woven, Or Combination Liners?

The ideal thermal insulation system is lightweight, captures air, and rejects water absorption while promoting the “wicking” of sweat. The best liners also resist shrinkage, withstand the effects of heat, and have high porosity or air permeability. There are a number of liner technologies that offer some or all of these advantages and they often deliver their protective value in different ways.

The Face Cloth Can Make a Big Difference

The part of your liner that you can usually see is the “face cloth”. The face cloth is generally the muscle, while the inside of your thermal barrier is the brain. The face cloth takes the abrasion and provides the seam strength to hold the whole thing together. Face cloths that “wick” perspiration off the body are more comfortable and some face cloths have the added advantage of being slippery. Liner systems using high-lubricity face cloths can reduce the strain of moving around and have been proven to be effective in reducing stress (IAFF/Indianapolis FD Study, 1999). Not all shiny liners have high lubricity.