Hotter Than Hot
FEATURES
PROTECTIVE CLOTHING
For temperatures measured in four digits, firefighters need special protection.
Generations of firefighters have tested themselves against smoke and heat, protected, for many years, by the simple barrier of a leather helmet and a canvas or rubber turnout coat. These were reliable allies against the punishing conditions of the vast majority of fires, good for temperatures reaching as high as 500° F in structural fires.
But physical bravado yields quickly to sheer survival needs when the flames burn hotter—as they do in chemical flash fires, petrochemical infernos, and plane crashes. And the protection needed becomes more sophisticated— changing from the familiar coat and helmet into a head-to-toe, space-age suit.
Even with wraparound insulation, no one would associate the word comfort with high-temperature protective suits. Even though a shiny outer layer on some of the suits reflects a lot of heat, the heat that gets through stays inside.
One thing remains the same as in the more familiar structural fire—size-up is important, to know what you’re dealing with and what level of protective clothing will deal with it best. Part of the size-up the identification of the sources of heat:
Radiant heat
When you feel the heat on your face as you arrive at the scene of a major fire, you’re experiencing radiant heat. Radiant heat travels in straight lines from its source in the form of waves or rays until it’s absorbed or reflected. If the surface it impinges on is dark in color and rough in texture, it will absorb the heat energy readily. Light and shiny surfaces reflect much of the heat energy away.
Ambient heat
The heat that’s diffused by conduction, convection, and radiation means throughout a particular environment is ambient heat. Different environments may exist next to each other or one within the other, and each can have a different ambient temperature. For example, the ambient temperature in a room used for drying materials might be 200° F, while in the surrounding occupancies it might be 75° F.
Conductive heat
When one object, such as a brick or a steel girder, transfers heat to another object, such as a human hand, it’s giving off conductive heat. High-temperature conductive heats sources can be handled for only a short interval. Even when a person wears the appropriate high-temperature protective clothing, there’s always a risk of injury if conditions exceed those described in a suit manufacturer’s recommendations.
Direct flame impingement
This is the most extreme instance of exposure to high temperatures for which protective clothing is designed. An example of direct flame impingement is a firefighter walking into a fully involved petroleum fire to shut off a valve, with open flame contact to the protective clothing. High-temperature gear is rated in terms of how long it can withstand a certain temperature, and the time is especially important in relation to direct flame impingement.
Approach Clothing
Approach clothing, for working within a couple of yards of a heat source, is ideal for use as the aluminized outer shell of chemical protective suits. The suits reflect radiant heat and resist chemical splashes. Approach suits are worn by industrial workers using chemical processors, large dip-tank operations, foundries and furnaces.
Short-term protection to 1,500° F
Proximity Clothing
The familiar “silver” proximity suit is the stereotypical high-temperature protective suit, intended for working close up to a heat source, as in crash rescue work. An aluminized outer layer reflects 95 percent of radiant heat, allowing prolonged exposure. That layer also provides some protection against steam and superheated liquids by sealing the woven material.
Power plants that have fire brigades need to be equipped with proximity suits for firefighting around superheated steam leaks. And the U.S. Nuclear Regulatory Commission recommends fire brigades at nuclear power plants have such clothing for the same reason. In industry, proximity suits may be used in the maintenance of furnaces, boilers, paint ovens, and process control equipment operating at petrochemical refineries.
Short-term protection to 1,500° F
Short-term protection to 500° F
Short-term protection to 1,000° F
Entry Clothing
Entry clothing is intended for use in situations that involve direct flame impingement or high radiant or ambient temperatures—situations in which the high heat surrounds the firefighter and is hard to get away from. Besides firefighting applications, the entry suits may be used in heat-treating operations; maintenance operations; and kiln entry in the glass, ceramic, and steel industries. They may also be used by aerospace contractors and furnace and forge operators.
All entry clothing must be used with self-contained breathing apparatus. The ample back pouch arrangements available from all manufacturers are designed to fit any SCBA.
The outer layer may be made of carbon fiber— which can resist repeated flame infringement—or of “white” woven fiberglass, which can resist the same temperatures as carbon fiber but must be replaced after a severe exposure.
- Single layer of aluminized fabric or fiberglass
- Available as coveralls or coat-and-pants combination
- Available with or without pouch for self-contained breathing apparatus
- Available with or without lift-front face shields
- Outer shell of aluminized fabric or fiberglass+
- Additional insulating layers
- Back pouch to accommodate SCBA
- Hood with a hard hat and suspension
- Ceramic lenses with heat-resistant gold plating in hood’s facepiece. The gold is 100 percent heat-reflective and reduces the temperature inside the helmet while reducing light transfer by only 40 percent. Sandwiching the gold between layers of ceramic or heat-resistant plastic will protect the gold plating from scratching; nonstratified lenses require frequent replacement.
Short-term protection to 1,500° F
Prolonged protection to 1,000° F
Short-term protection to 1,000° F
Short-term protection to 1,500° F
- Outer layer of woven fiberglass or carbon fiber cloth
- Additional layers of insulating material (more than are found in proximity suits)
- Back pouch to accommodate SCBA
- Hood with a hard hat and suspension
- Ceramic lenses with heat-resistant gold plating in hood’s facepiece
