This glossary contains definitions for some of the most common technical terms relating to thermal protection and protective apparel.
Categories
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| Thermal Characteristics |
| Arc Thermal Performance (ATPV): |
A reported value from electric arc testing. Basically, it is the measure of how much heat can be exposed to a flame resistant garment before a second degree burn injury is expected to occur. |
| Electric arc: |
The passage of substantial electric current through ionized air. |
| Flame resistant: |
The characteristic of a fabric to resist ignition and to self extinguish if ignited. |
| Flame retardant: |
A chemical substance used to impart flame resistance - not part of the basic fibers chemistry. Flame retardant treatments can diminish overtime or with use. |
| Flammability (Vertical Flame Test): |
Measures char damage length, afterflame and afterglow time on a 3" x 12" fabric sample exposed to flame at its lower edge for 12 seconds. |
| Flash-fire: |
A sudden, unexpected and intense fire caused by ignition of flammable solids, liquids, gases or dusts. |
| Inherently Flame Resistant: |
The flame resistance properites are a result of the chemistry of the material (fiber). Flame resistance will not diminish over time or with use. |
| Limiting Oxygen Index (LOI): |
Determines minimum oxygen content (%) in air that will sustain combustion of a material. |
| Mannequin Test for Predicted Body Burn Injury: |
Predicts second- and third-degree burn injury for garments on an instrumented mannequin in a controlled flash-fire exposure. |
| Stoll Curve: |
A plot of thermal energy and time used to predict the onset of pain sensation and a second degree burn, in human tissue |
| Thermal Conductivity: |
Rate at which heat will flow through a material. |
| Thermal Protection: |
The resistance to flame and associated thermal transfer through the garment. |
| Thermal Protective Performance (TPP): |
A fabric specimen is exposed with a combination of radiant and convective energy. The total energy required to cause second-degree burn injury to human tissue is determined based on heat transfer through the fabric specimen and the Stoll second-degree burn criteria. Single and multiple layer fabric specimens can be tested. |
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| Standard-Setting Organizations |
| American Society of Testing of Materials (ASTM) |
ASTM publishes both performance specifications and test methods for evaluating protective clothing and equipment. |
| Canadian Government Standards Board (CGSB) |
CGSB is a voluntary compliance organization that is sponsored by the Canadian government. |
| National Fire Protection Association (NFPA) |
NFPA writes voluntary compliance standards related to the Fire Service and other industries. |
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| Fabric Physical Properties |
| Air permeability: |
Measure of air flow through a fabric. |
| Anti-static Performance: |
Measures attraction and dissipation of electric charge on fabric |
| Basis Weight: |
Weight of fabric per unit area, usually oz/yd2 |
| Bending Stiffness: |
Force required to bend fabric. |
| Breaking Load: |
Load required to break (pull apart) fabric |
| Bursting Strength (Mullen Burst): |
Force required to rupture a knit fabric with an expandable diaphram. |
| Denier (Yarn): |
Weight in grams of 9000 meters of yarn. |
| Denier Per Filament: |
Weight in grams of 9000 meters of a single filament. |
| Light-fastness: |
Measures change in knit or woven fabric color after exposure to light from a xenon arc. |
| Staple cut length: |
Length of uncrimped staple fibers. |
| Surface Appearance: |
Evaluates knit or woven fabric smoothness after repeated home launderings. |
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| Electricity Definitions |
| Alternating Current (AC): |
Current flows back and forth (a cycle) through a conductor. In each cycle, the electrons flow first in one direction, then the other. |
| Direct Current (DC): |
current flows in only one direction |
| Electricity: |
the flow of an atoms electrons through a conductor |
| Ground: |
A conducting connection – which may or may not be intentional – between an electrical circuit or equipment and the earth, can be via some conducting body that leads to the earth |
| Hertz (Hz): |
number of cycles per second |
| Ohm's Law: |
Current = Voltage/Resistance |
| Resistance: |
Anything that impedes the flow of electrons through a conductor and is measured in ohms |
| Voltage: |
The force that causes electricity to flow through a conductor and is measured in volts. |
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| Learn more about the above Standard-setting organizations or the Apparel specifications established by these organizations. |
