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Glossary PACKAGE MARKINGS The descriptive name, instructions, cautions, weight, or specification marks required on the outside of containers of hazardous materials. PAINT SPRAYING Used in many industries, including automotive, aircraft, boating and appliances, paint spraying may pose inhalation and skin contact hazards from solvents, pigments and additives. PANIC HARDWARE Hardware used in many public buildings and mounted on exit doors that permits the door to open when pressure is applied against the hardware. PAPRS (POWERED AIR PURIFYING RESPIRATORS) Breathing masks with specific chemical cartridges designed to either filter particulates or absorb contaminants before they enter the worker's breathing zone. PAPR's use portable motors to force air through the filtering/purifying cartridges; intended for use only in atmospheres where the chemical hazards and concentrations are known. PARALLEL OPERATION (also volume) Operation of pump when each of its impellers is receiving water from a common source and contributing volume directly to the discharge. PARAPET Extension of a firewall above a roof to prevent fire from extending. See Fire Wall. PARASITE Any organism that lives in or on another organism without providing benefit in return. PART PAID/PART TIME (Call) Firefighters who are paid on the basis of the time that they are used as substitutes for full-time personnel. PARTNER DECONTAMINATION The process whereby the entry team members, upon exiting the hot or exclusion zone, will decontaminate (gross) each other, avoiding unnecessary or excessive chemical exposure to decontamination team members. PASCAL The pressure obtained when a force of one Newton acts on an area of one square meter. PASTE A mixture such as flour and water boiled together that will stick paper together, stick it to a wall, or serve as a medium for the application of certain pesticide poisons. PATCHING The use of compatible plugs or materials to reduce or temporarily stop the flow of substances from small holes, rips, tears, or gashes in containers. The repaired container may not be reused without proper inspection and certification. PATHOGENIC AGENT Biological agents capable of causing serious diseases. PATHOGENS Any disease-producing organisms, including viruses; any organism (usually living) capable of producing serious disease or death, such as bacteria, fungi, and viruses. PATHWAYS OF DISPERSION The mode (water, groundwater, soil, and air) by which a chemical moves through the environment. PATTERN The adjustment of a stream from fire nozzle; shape of the water stream as it is discharged from a fog nozzle. PBI Polybenzimidazole, a synthetic polymer designed for high temperature applications. Used as an adhesive, composite, and a coating with metals and as a fabric for structural fire fighting gear. PDP Abbreviation for Pump Discharge Pressure. PEAK HOURLY CONSUMPTION Maximum amount of water used during any hour of a day. PEDESTAL, CONTROL A panel on which all of the controls and instruments are mounted for the purpose of controlling, hoisting, extending, and rotating aerial ladders. PEL (PERMISSIBLE EXPOSURE LIMIT) Abbreviation for Permissible Exposure Limit. Term used by OSHA for its health standards covering exposures to hazardous chemicals. PEL generally relates to legally enforceable TLV limits. An occupational health term used to describe exposure limits for employees. Usually described in time weighted averages (TWA) or short term exposure limits (STEL). PENDANT SPRINKLER An automatic sprinkler head designed for placement and operation with the head pointing downward from the piping. PENETRATION The flow of a liquid through closures, porous materials, seams and pinholes or other imperfections in a protective clothing material on a nonmolecular level. PENETRATION (SUIT) The movement of a material through a suit’s closures, such as zippers, buttonholes, seams, flaps, or other design features of chemical protective clothing and through punctures, cuts, and tears. PENETRATION RATE The time required for a material to move through a suit’s closures. PERCUTANEOUS AGENT Able to be absorbed through the body. PERMEATION The process by which a chemical moves through a protective clothing material on a molecular level. Permeation involves the following:
A chemical action involving the movement of a chemical, on a molecular level, through intact material. PERMEATION RATE The rate at which the challenge chemical permeates the fabric. PERMISSIBLE EXPOSURE LIMIT (PEL) The maximum time-weighted concentration at which 95% of exposed, healthy adults suffer no adverse effects over a 40-hour work week and are comparable to ACGIH's TLV/TWA. PELs are used by OSHA and are based on an eight-hour, time-weighted average concentration. PERSISTENT AGENT An agent that upon release retains its casualty-producing effects for and extended period of time, usually anywhere from 30 minutes to several days; usually has a low evaporation rate and its vapor is heavier than air; vapor cloud tends to hug the ground; considered to be a long-term hazard; an agent that remains in the target area for loner periods of time. Hazards from both vapor and liquid may exist for hours, days, or in exceptional cases, weeks, or months after dissemination of the agent. As a general rule, persistent agents duration will be greater than 12 hours. PERSISTENT CHEMICALS A substance which resists biodegradation and/or chemical oxidation when released into the environment and tends to accumulate on land, in air, in water, or in organic matter. PERSONAL PROTECTIVE EQUIPMENT The equipment provided to shield or isolates a person from the chemical, physical, and thermal hazards that may be encountered at a hazardous material incident. PPE includes both personal protective clothing and respiratory protection. Adequate personal protective equipment should protect the respiratory system, skin, eyes, face, hands, feet, head, body, and hearing. PESTICIDES Chemical or mixture of chemicals used to destroy prevent, or control any living organism considered to be a pest. PETN Pentaerythritol Tetra nitrate; mainly used in the manufacture of detonating fuses (Primacord). PH pH is a measure of the acidity or basicity of a water based solution. The scale ranges from 0 to 14 with pH 7 as neutral, acids below pH 7 and bases above pH 7. It is technically the negative logarithm of the hydrogen ion concentration. Sometimes referred to as the "Power of Hydrogen" since a change in the pH of 1 is equal to a change in concentration of ten times. Like wise a change in pH of 2 is a change of concentration of 10x10x10 or 100; a pH change of 3 is a concentration change of 10x10x10, and so on. This is an exponential relationship and pH is really the mathematical "power" or exponent of the concentration. PHASES OF FIRE A degree of flame progression. Phase I, fire in incipient stage and beginning to grow. Phase II, freeburning, flame propagation is at its greatest. Phase III, oxygen is deficient in the burn area, producing a smoldering phase. PHONETIC ALPHABET An alphabet devised by the International Civil Aviation Organization (ICAO), used in radio-telephone conversations, in which a word is used phonetically in the place of letters. Example, A is alpha. PHOTO IONIZATION The formation of an ion by the bombardment of an atom by ultraviolet light. The bombardment "knocks" an electron off the atom. PHYSICAL PROPERTIES Properties of a material that relate to the physical states common to all substances, i.e. a solid, a liquid, or a gas. A property of matter that describes only its condition, not the way it reacts with other substances. Examples are size, density, color, and electrical conductivity. PHYSICAL STATE The physical state or form (solid, liquid, gas) of the material at normal ambient temperatures (68° F to 77° F). PHYSICAL-CHEMICAL PARAMETERS Values for physical or chemical properties of a permeant or polymer, or both, such as solubility parameters, molecular weight, vapor pressure, etc. PHYSIOLOGICAL ACTION Most toxic chemical agents are used for their toxic effects that are to produce a harmful physiological reaction when applied to the human body externally, or when breathed, or taken internally; the reaction of chemical agents, within the body or on the body, is the physiological action. PHYSIOLOGY The science dealing with the normal functions of living things or their organs (i.e., physiology of the blood). PICKUP PLATE A sloped plate and structure of a trailer, located forward of the kingpin and designed to facilitate engagement of fifth wheel to kingpin. PICO Metric prefix for 10-12, 0.000 000 000 001, abbreviated p. PID Abbreviation for Photo Ionization Detector. A monitoring device, which ionizes sample using ultraviolet light. Electrons "knocked" loose from the sample are collected and electronically amplified to provide the user with a signal or display value. Typically these instruments are used for materials in the concentration range of 0.10 to 2,000 ppm. PIERCING NOZZLE Nozzle with an angled, case-hardened steel tip that can be driven through a wall, roof, or ceiling to extinguish hidden fire. Also called Puncture Nozzle. PIEZOMETER TUBE An instrument joined to a pipe or hose for indicating the pressure of a liquid or a gas; device that uses the heights of liquid columns to illustrate the pressures existing in hydraulic systems. PIG (PIPELINE) A solid plug inserted into a pipeline either to separate products or to clean and purge the line. PIGGYBACK TRANSPORT Type of shipping in which bulk containers from one mode, such as highway transportation, are placed on flat cars or container ships for transportation by another mode, such as rail or marine. PIKE POLE A sharp prong and metal hook on a wood, metal, plastic, or fiberglass handle used for pulling, dragging, probing, and other purposes. PIN LUG COUPLINGS Hose couplings with round lugs in the shape of a pin. PINTLE See Hitch. PIO See Public Information Officer. PIPELINE A way to transport a product. PISTON PUMP A positive-displacement pump using one or more reciprocating pistons to force water from the pump chambers. PISTON VALVE Valve with an internal piston that moves within a cylinder to control the flow of water through the valve. PITOT TUBE A curved tube having an opening that is inserted into a stream of water and to which a pressure gauge is attached that indicates the discharge pressure of the stream; instrument containing a Bourdon tube that is inserted into a stream of water to measure the velocity pressure of the stream; the gauge reads in units of pounds per square inch (psi) or kilopascals (kPa). PLACARDS 10-3/4 in. (273.0 mm)-square diamond markers required on the transporting vehicle such as a truck or tank car, or a freight container 640 cu ft (18.lm3) or larger. PLANNED REMOVAL The removal of released hazardous substances from the environment within a non-immediate, long term, time period. Under CERCLA, actions intended to minimize increases in exposure such that time and cost commitments are limited to 6 months and/or one million dollars. PLANNING SECTION Responsible for the collection, evaluation, dissemination and use of information about the development of the incident and the status of resources. Includes the Situation Status, Resource Status, Documentation, and Demobilization Units as well as Technical Specialists. PLASTER HOOK A barbed collapsible hook on a pole to permit puncturing and pulling down materials. PLASTIC A material that contains, as an essential ingredient, one or more organic polymeric substances of large molecular weight, is solid in its finished state, and, at some stage in its manufacture of processing into finished articles, can be shaped by flow. PLATES Construction members used to form the top and bottom of a frame wall. PLATOON The entire shift of a fire department; may, however, indicate only those in one section or district who are on or off duty. PLAY A STREAM To direct a stream of water onto a fire or a desired point of application. PLAYPIPE Used to describe the base part of a three-part nozzle, from the coupling to the shutoff. PLUG A fire hydrant. PLUG PRESSURE The pressure available for a hose stream without the application of a fire pump. PLUGGING The use of compatible patches or materials to reduce or temporarily stop the flow of liquids from small holes, rips, tears, or gashes in containers. The repaired container may not be reused without proper inspection and certification. PLUME A vapor, liquid, dust, or gaseous cloud formation which has shape and buoyancy. PNEUMATIC POWER Power derived by using the properties of compressed gases either at rest or in motion. Generally used in combination with a pressure regulator. POINT OF ORIGIN The exact location at which a particular fire started. POISON Any substance (solid, liquid, or gas), which by reason of an inherent deleterious property tends to destroy life or impair health. POLAR SOLVENT LIQUIDS Those liquids that mix (are miscible) with water. POLARIZED COUPLERS Fittings for connecting of air brake lines between vehicles. The service and emergency couplings are unilateral and will not mate with each other. POLE The sliding pole from upper stories to the apparatus area of a fire station; ladder poles, stay poles. POLLUTANT A substance or mixture, which after release into the environment and upon exposure to any organism will or may reasonably be anticipated to cause adverse effects in such organisms or their offspring. POLLUTANT TRANSPORT An array of mechanisms by which a substance may migrate outside the immediate location of the release or discharge of the substance. For example, pollution of groundwater by the migration of hazardous wastes from a landfill. POLYESTER Man-made fiber with a high level of strength, stability and abrasion resistance. POLYMER A substance consisting of molecules characterized by repetition (neglecting ends, branches, junctions, and other minor irregularities) of one or more chemically bonded types of monomeric units. A giant, long chain of molecules having extremely high molecular weights made up of many repeating smaller units called monomers or commoners. POLYMERIZATION A chemical reaction, usually carried out with a catalyst, heat or light-and often under high pressure-that generates high temperature and may be violent when uncontrolled. A chemical reaction in which one or more small molecules combine to form larger molecules. A hazardous polymerization is such a reaction that takes place at a rate that releases large amounts of energy that can cause fires or explosions or burst containers. Materials that can polymerize usually contain inhibitors that can delay the reactions. POLYVINYL ALCOHOL A water-soluble polymer made by hydrolysis of a polyvinyl ester (such as polyvinyl acetate); used in adhesives, as textile and paper, and for emulsifying, suspending, and thickening of solutions. Abbreviated PVA. POMPIER An obsolete scaling ladder with a single beam with rungs protruding from each side of the beam and a large curved metal hook that can be placed over windowsills when used for climbing. PORT A place where ships and boats can load or unload or be sheltered from storms; a harbor. An opening in the side of a ship to let in light and air or for loading and unloading. The left side of a ship when facing the bow. An opening in a container. PORTABLE BASIN See Portable Tank. PORTABLE CONTAINER A container designed to be moved readily, as distinguished from containers designed for stationary installations. Portable containers, designed for transportation, filled to their maximum filling limit, include cylinders, cargo tanks, and portable tanks, all three of which are defined separately under NFPA 58. Containers which are designed to be "readily" moved from one usage to another, but substantially empty of product, are defined under NFPA 58 as portable storage containers. PORTABLE HYDRANT See Manifold. PORTABLE LADDER PIPE A portable, elevated master stream device clamped to the top two rungs of the aerial ladder when needed and supplied by a 3 or 31/2-inch (77 mm or 90 mm) fire hose. PORTABLE PUMP A small gasoline-driven fire pump designed to be transported on fire apparatus and capable of supplying streams through hose or relaying supply to a fire department pumper. PORTABLE SOURCE Water that is mobile and may be taken directly to the location where it is needed. This may be a fire department tanker or some other vehicle that is capable of hauling a large quantity of water. PORTABLE STORAGE CONTAINER A container similar to but distinct from those designed and constructed for stationary installation, designed so that it can be moved readily over the highways, substantially empty of liquid, from one usage to another. Such containers either have legs or other supports attached, or are mounted on running gear (such as a trailer or semitrailer chassis) with suitable supports of the fold-down type, allowing them to be placed or parked in a stable position on a reasonably firm and level surface. For large volume, limited duration product usage (such as construction sites and on site normally 12 months or less), portable storage containers function in lieu of permanently installed stationary containers. PORTABLE TANK Collapsible storage tank used during a relay or shuttle operation to hold water from water tanks or hydrants. This water can then be used to supply attack apparatus. Also called Catch Basin, Fold-a-Tank, Portable Basin, Portable Water Tank, or Porta-Tank. POSITION Specific assignment during a fire operation. POSITIVE-DISPLACEMENT PUMP Any number of a variety of piston or rotary-gear pumps that move a given quantity of water through the pump chamber with each stroke or cycle; self-priming pump that moves a given amount of water or hydraulic oil through the pump chamber with each stroke or rotation; pumps used as hydraulic pumps on aerial device hydraulic systems and for priming pumps on centrifugal fire pumps. POST DECONTAMINATION Usually the period of time after decontamination when the person is allowed to rest and take fluids to replace the lost electrolytes. Sometimes the debriefing period. POST FIRE OPERATIONS Includes overhaul to search for and extinguish hidden fires, determine the cause of fire, identify and preserve evidence of arson, make the building and area safe, return to quarters, prepare equipment for future use, and write reports. POST INCIDENT ANALYSIS A formal evaluation conducted after an incident to determine strengths and weaknesses of the participating members/companies/departments. The termination phase of an incident that includes completion of the required forms and documentation for conducting a critique. POST INDICATOR VALVE (PIV) A post-type valve that provides a visual means of indicating "open" or "shut" position; found on the supply main of installed fire protection systems. POST-CONSUMER RECYCLED (PCR) CONTENT In the case of Tyvek® spunbonded olefin fabrics, the amount of polyethylene recovered from used plastic containers that, after cleaning, is used to make certain Tyvek® products. POWDER A solid reduced to dust by pounding, crushing, or grinding. POWER TAKE-OFF (PTO) Rotating shaft that transfers power from the engine to auxiliary equipment. POWER TRAIN Means of transferring power from an engine to a pump; includes all power-transmitting components. PPE (PERSONAL PROTECTIVE EQUIPMENT OR PERSONAL PROTECTIVE ENSEMBLE) Personal safety equipment to include gloves, helmets, glasses, hard-toed shoes, garments, face shields and ear plugs; may include approved hood, gloves, helmet, boots, pants and coat. PPM Abbreviation for Parts Per Million. Refers to the parts of one material in a whole of a million. For example one red marble in a box containing 999,999 other white marbles would be 1 ppm red marbles. Typically used to describe very dilute solutions or air born contaminants. PRE-ACTION SYSTEM A type of automatic sprinkler system in which thermostatic devices are employed to charge the system with water before individual sprinkler heads are fused. PRE-CONNECT Attack hose connected to a discharge when the hose is loaded; this shortens the time it takes to deploy the hose for fire fighting; soft intake hose that is carried connected to the pump intake. PRE-DECONTAMINATION The physical removal of excess layers of protective clothing (outer boots, gloves) prior to exiting the hot zone and entering the decontamination corridor. PRE-FIRE PLANNING The act of preparing to fight a fire in a particular building or group of buildings by advance planning of possible fire fighting operations. PRE-SERVICE TESTS Tests performed on fire pumps or aerial devices before they are placed into service. These tests are broken down into manufacturer's tests, certification tests, and acceptance tests. PRECIPITATE Result when a solution of one chemical is combined with a solution of another chemical and an insoluble material is produced. PRECONNECTED A procedure whereby hose is connected either to the intake or the outlet of the pump before a fire, to expedite hose operations and fire fighting procedures. PRECURSOR A chemical substance required for the manufacture of chemical agent. PRESSURE A force applied over a given area. Force per unit area measured in pounds per square inch (psi) or kilopascals (kPa). PRESSURE GOVERNOR Pressure control device that controls engine speed and therefore eliminates hazardous conditions that result from excessive pressures. PRESSURE OPERATION Operation of a two (or more) stage centrifugal pump in which water passes consecutively through each impeller to provide high-pressures at a reduced volume. Also called Series Operation. PRESSURE REGULATOR A device used to maintain a constant pressure within a pump under all operating conditions. PRESSURE RELIEF DEVICE An automatic device designed to release excess pressure from a fire pump. A spring-loaded valve, generally used on a reciprocating pump for providing relief from excessive pressures (also weather pressures). Placed on the discharge side of the pump. In case of too much backpressure, the seat of the valve lifts and fluid is allowed to escape to the intake side of the pump. PRESSURE RELIEF VALVE A type of pressure relief device designed to open and close to maintain internal fluid pressure. Pressure relief valves are divided into the following types: External Pressure Relief Valve, Flush Type Full Internal Pressure Relief Valve, Full Internal Pressure Relief Valve, Internal Spring-Type Pressure Relief Valve, and Sump-Type Full Internal Pressure Relief Valve. PRESSURE TANK A system of storing water in tanks under pressure for fire fighting purposes or for fire protection purposes; used instead of elevated tanks or auxiliary pumps in private fire protection. PRIMARY FEEDER Large pipes (mains), with relatively widespread spacing, that convey large quantities of water to various points of the system for local distribution to the smaller mains. PRIME To remove all air from a pump and intake hose in preparation for receiving water under pressure. PRIMER OIL TANK A tank of oil used for sealing and lubricating a priming pump. PRIMING A procedure of filling the pump with water in preparation for pumping. PRIMING PUMP Any number of a variety of small positive-displacement pumps or devices used to prime a centrifugal pump by removing or replacing the air to permit water to flow into the pump impeller; a small positive-displacement pump used to evacuate air from a centrifugal pump housing and hard suction hose; evacuating air allows the centrifugal pump to receive water from a static water supply source. Also called Primer. PRIVATE CONNECTION Connections to water supplies other than the standard municipal water supply system; may include connection within a large industrial facility, a farm, or a private housing development. PRIVATE HYDRANT Hydrant provided on private property or on private water systems for the protection of private property. See Yard Hydrant. PROCESS SAFETY MANAGEMENT (PSM) The application of management principles, methods and practices to prevent and control releases of hazardous chemicals or energy. Focus of both OSHA 1910.119&emdash;Process Safety Management of Highly Hazardous Chemicals, Explosives and Blasting Agents and EPA Part 68&emdash;Risk Management Programs for Chemical Accidental Release Prevention. PRODUCT (CHEMICAL) STRESSOR Any chemical, which causes a reaction with or within the container in which it is stored. The reaction causing a failure or possible failure of the container such as an acid in an unprotected aluminum tank. PROPORTIONER A device for inducing the correct amount of agent into streams of water, especially for foam and wetting agents. PROPORTIONING VALVE Valve used to balance or divide the air supply between the aeration system and the discharge manifold of a foam system. PROPRIETARY SYSTEM A fire protection system that is owned and operated by the owner of the property. PROTECTIVE CLOTHING A garment used for the purpose of isolating parts of the body from potential contact with a hazard. PROTECTIVE CLOTHING MATERIAL Any material or combination of materials used in an item of clothing for the purpose of isolating parts of the body from a potential hazard. PROTECTIVE ENSEMBLE The combination of head, hand, face, foot and body protective equipment-including respiratory protection and accessories such as cooling and communications devices-used together to protect against specific. PROTEIN FOAM Protein foams are chemically broken down (hydrolyzed) protein solids. The end product of this chemical digestion is protein liquid concentrate. PROXIMITY SUIT A suit that provides short duration and close proximity protection at radiant heat temperatures as high as 2,000•F and may withstand some exposure to water and steam. Respiratory protection must be provided with proximity suits. PSI (POUNDS PER SQUARE INCH) Pressure measurement usually used for pump pressure, nozzle pressure, friction loss, pressure loss, etc. PSIA See Absolute Pressure for definition. PSIG Pounds per square inch gauge. PSTN (PESTICIDE SAFETY TEAM NETWORK) Regional teams of the National Agricultural Chemical Association designed to assist with pesticide incidents. PTO Abbreviation for Power Take-Off. PUBLIC INFORMATION OFFICER A public official usually part of an emergency management group whose function is to coordinate emergency information releases to the media or to the public. PUBLIC PROTECTIVE ACTIONS The strategy used by the Incident Commander to protect unexposed people from the hazardous materials release by evacuating or protecting-in-place. This strategy is usually implemented after the IC has established an isolation perimeter and defined the Hazard Control Zones for emergency responders. PULMONARY Pertaining to the lungs. PULMONARY RESUSCITATION See artificial resuscitation. PUMP AND ROLL Ability of an apparatus to pump water while the vehicle is in motion. PUMP CAN Term for extinguisher; generally a water pump-type extinguisher. PUMP CAPACITY RATING Maximum amount of water a pump will deliver at the indicated pressure. PUMP CHARTS Charts carried on a fire apparatus to aid the pump operator in determining the proper pump discharge pressure to use when supplying hoselines. Also called Hydraulic Calculation Charts. PUMP DISCHARGE PRESSURE (PDP) Actual velocity pressure (measured in pounds per square inch) of the water as it leaves the pump and enters the hoseline. PUMP DRAIN Drain located at the lowest part of the pump to help remove all water from the pump; eliminates the danger of damage due to freezing. PUMP OFF LINE A pipeline that usually runs from the tank discharge openings to the front of the trailer. Most pumps are mounted on the tractor. PUMP OPERATOR A firefighter charged with operating the pump and determining the pressures required to operate it efficiently. PUMP PANEL An instrument panel located on the pump operator's side of the apparatus. PUMP TANK A small, water fire extinguisher having a built-in hand pump and an attached hose and nozzle. PUMPER/TANKER A mobile water supply apparatus equipped with a fire pump; term used to differentiate a fire pump equipped mobile water supply apparatus whose main purpose is to attack the fire. PUMPERS, CLASSIFICATIONS OF Class A - A pumper that will deliver its rated capacity of 150 psi net pump pressure at a lift of not over 10 feet with a motor speed of not over 80% of the certified peak of the brake horsepower curve and deliver 70% of rated capacity at 200 psi and 50% of rated capacity at 250 psi. Class B - A pumper that will deliver its rated capacity at 120 psi net pump pressure with not over 10 foot lift and motor speed not exceeding 80% of the certified peak of the brake horsepower curve and deliver 50% of its rated capacity at 200 psi and 33 1/3% of its rated capacity at 250 psi. PUMPING APPARATUS A fire department apparatus that has the primary responsibility to pump water. PUNCTURE NOZZLE A specially designed nozzle for puncturing and inserting into walls to extinguish hidden fires. Also Bayonet or Piercing Nozzle. PURGE TIME In an intermittent contact test, the time immediately following the termination of the contact time when the test chemical is removed from the challenge side chamber and air or nitrogen is blown over the outside surface of the protective clothing material. PURGING Totally enclosed electrical equipment is protected with an inert gas under a slight positive pressure from a reliable source. The inert gas provides positive pressure within the enclosure and minimizes the development of a flammable atmosphere. Used in Class I, Division 1 atmospheres at fixed installations. PYROLYSIS A chemical decomposition or breaking apart of molecules produced by heating. PYROMANIA An irresistible impulse to start fires. PYROMETER A device used for recording temperatures. Pyrometers connected to thermocouples record the heat at various points. See Thermocouple. PYROPHORIC Materials that ignite spontaneously in air below 130•F (54•C). PYROPHORIC LIQUID Any liquid that ignites spontaneously in dry or moist air at or below 130 degrees F (54 degrees C). PYROPHORICS Chemicals that will ignite or react violently on contact with air or oxygen; must be maintained under an inert atmosphere. PYROXYLIN PLASTIC A nitrocellulose plastic material that is extremely combustible and susceptible to deterioration and self-ignition; produces toxic fumes when burned. |
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