fire area An area of a building that is separated from the remainder of me building by construction, having a fire resistance of at least one hour and having all communicating openings properly protected by an assembly having a fire rating of at least one hour.
fire extinguishers, classes (Portable Hand Held) Class A extinguishers rated for Class A fires may contain waier, aqueous-film-forming foam, dry chemical, or a halogen compound; Class B extinguishers for Class B fires may contain carbon dioxide, dry chemical, aqueous-film-fonning foam, or halogenated agents; Class C extinguishers for Class C fires may contain carbon dioxide, dry chemical, or a halogenated compound; and Class D extinguishers for use on Class D fires contain specially prepared materials, such as Met-L-X powder, T.E.C. powder, etc.
fire resistance rating The time period, in hours or fractions thereof, that a building member or assembly will resist a code-specified fire test without failure. For example, a 2-hour rating indicates that the assembly withstood the standard test for greater than two hours without failure by any of the failure criteria listed in the fire test protocol.
fire separation The distance in feet measured from the building face to the closest interior lot line, to the center of a street or public way, or to an imaginary line between two buildings on the same property.
fire triangle The three elements that must be present in the right proportion for a fire to exist: oxygen (or an oxidizing agent), fuel (or a reducing agent), and heat. Keeping the three elements of the fire triangle apart is the key to preventing fires, and removing one or more of these elements is the key to extinguishing fires that do start.
fire watch Individual provided with fire extinguishing equipment and training in its use who is posted (1) in the immediate area of welding or cutting operations when other than a minor fire might develop; (2) where there is an appreciable amount of combustible building material nearby; (3) where sparks could ignite nearby combustibles; or (4) where combustible materials are adjacent to the opposite side of metal partitions, walls, ceilings, or roofs and are likely lo be ignited by conduction or radiation.
fires Classes of fires: Class A fires are fires in ordinary combustible materials (e.g., paper, wood, cloth); Class B fires are those in combustible or flammable liquids, flammable gases, greases, and similar materials; Class C fires are those in electrical equipment; and Class D fires are those in combustible metals (e.g.. magnesium, sodium, potassium, etc.).
fit check (Respiratory Protection) Action by a respirator user to determine if the respirator is properly seated to the face. A positive or negative pressure check is made to ensure proper respirator facepiece seal. See user seal check.
fit factor (Respiratory Protection) A measure of how well a respirator fits as determined by a quantitative fit test. The ratio of the test agent concentration outside the respirator to the agent concentration inside the respirator.
fit test (Respiratory Protection) A protocol for determining an individual's ability to obtain a good fit with a particular size and style of respirator. Fit testing may be qualitative or quantitative.
fixed contamination (Radioactivity) Contamination that is unlikely to become airborne so that it may be inhaled or unlikely to adhere io the hands on being touched, so that it is not likely to be ingested.
flame ionization detector A carbon detector that relies on the detection of ions formed when a carbon-containing material, such as a volatile or gaseous hydrocarbon, is burned in a hydrogen-rich flame. This detector is commonly used in a gas chromatograph to detect and quantitate organic compounds. It is also employed in some portable instruments.
flame photometric detector A detection system based on the luminescent emissions between 300 and 425 nanometers when sulfur compounds are introduced into a hydrogen-rich flame. An optical filter system is used to differentiate the sulfur compounds present from other materials. This detector finds application in gas chromatography.
flammable liquid Liquid having a flash point below IOO¢XF and a vapor pressure not exceeding 40 pounds per square inch (absolute) at 100¢XF is a Class I flammable liquid. Class I flammable liquids are subdivided inio Class IA, which have a flash point below 73¢XF and a boiling point below 100¢XF; Class IB. which have a flash point below 73¢XF and a boiling point above 100¢XF; and Class 1C, which have a flash point at or above 73¢XF and below 100¢XF.
flammable range All concentrations of a mixture of a flammable vapor or gas in air in which a flash will occur or a flame will travel if the mixture is ignited. The lowest percentage at which this will occur is the lower explosive limit, and the highest percentage is the upper explosive limit. The difference between the lower and upper flammable limits. See flammable limits.
fluidization A technique in which finely divided solids are caused to behave like a fluid by suspending them in a moving gas or liquid. An example is the fluid catalytic cracking process in petroleum refineries.
fluorescence The emission of electromagnetic radiation, especially that of visible light, as a result of the absorption of electromanetic radiation, and persisting only as long as the stimulating radiation is continued.