COF C-91 questions and answers with
solutions 2025
BOILING POINT - ANSWER The temperature at which the vapor pressure of a liquid equals the
atmospheric pressure of 14.7 pounds per square inch (psia) or 760 mm of mercury. Where a boiling
point is unavailable for the material in question or for mixtures which do not have a constant boiling
point, for the purposes of this classification, the 20-percent evaporated point of a distillation performed
in accordance with ASTM D 86 shall be used as the boiling point of the liquid.
CEILING LIMIT - ANSWER The maximum concentration of an airborne contaminant to which one may be
exposed shall be as established by the regulations of the United States Department of Labor, as set forth
in 29 CFR Part 1910.1000, or if not listed therein, the ceiling Recommended Exposure Limit (REL-C)
concentrations published by the U.S. National Institute for Occupational Safety and Health (NIOSH), the
Threshold Limit Value — Ceiling (TLV-C) concentrations published by the American Conference of
Governmental Industrial Hygienists (ACGIH), the ceiling Workplace Environmental Exposure Level (WEEL-
Ceiling) Guides published by the American Industrial Hygiene Association (AIHA), or other approved
standard.
CHEMICAL - ANSWER An element, chemical compound or mixture of elements or compounds or both.
CHEMICAL NAME - ANSWER The scientific designation of a chemical in accordance with the
nomenclature system developed by the International Union of Pure and Applied Chemistry, the Chemical
Abstracts Service rules of nomenclature, or a name that will clearly identify a chemical for the purpose of
conducting an evaluation.
CLOSED CONTAINER - ANSWER A container sealed by means of a lid or other device capable of
preventing the escape of liquid, vapor or dusts in the ordinary course of storage, handling or use.
CONTAINER - ANSWER For solid and liquid hazardous materials, a vessel of 60 gallons or less in capacity
used for storage or transportation. For compressed gases, a cylinder, pressure vessel or tank designed for
pressures greater than one atmosphere at 68°F. Pipes, piping systems, engines and engine fuel tanks
associated with solid or liquid hazardous materials or compressed gases, shall not be deemed to be
containers if in active use.
CONTAINMENT SYSTEM - ANSWER A gas-tight recovery system comprised of devices or equipment
which, when placed over or around the portion of the compressed gas container that is leaking, stops or
controls the escape of gas from the container.
, CONTAINMENT VESSEL - ANSWER A gas-tight vessel which, when installed or placed over or around a
leaking compressed gas container, confines the container and the gas leaking there from.
CONTROL AREA - ANSWER Spaces within a building that are enclosed and bounded by exterior walls, fire
walls, fire barriers and roofs, or a combination thereof, where quantities of hazardous materials not
exceeding the maximum allowable quantities per control area are stored, handled or used, including any
dispensing.
DESIGN PRESSURE - ANSWER The maximum gauge pressure that a pressure vessel, device, component or
system is designed to withstand safely under the temperature and conditions of use.
DETACHED BUILDING - ANSWER A separate single-story building, without a basement or crawl space,
used for the storage, handling or use of hazardous materials and located an approved distance from
other buildings or structures.
DISPENSING - ANSWER The pouring or transferring by other means of any material from a container,
tank or similar vessel, which would release dusts, fumes, mists, vapors or gases to the atmosphere,
unless such release is prevented by a device, equipment or system designed for that purpose.
EXCESS FLOW CONTROL - ANSWER A fail-safe system or other approved device, equipment or system
designed to shut off flow caused by a rupture in a pressurized piping system.
EXHAUSTED ENCLOSURE - ANSWER A device, typically consisting of a hood equipped with a fan that
serves to capture and exhaust fumes, mist, vapors and gases generated at a workstation or other local
environment. An exhausted enclosure does not include a room provided with general ventilation.
EXOTHERMIC - ANSWER A process or reaction that releases energy usually in the form of heat, but also
in form of light e.g. a spark, flame, or explosion.
EXPLOSION - ANSWER An effect produced by the sudden violent expansion of gases, whether or not
accompanied by a shock wave or disruption, of enclosing materials, including the effects of chemical,
physical, and atomic sources.
solutions 2025
BOILING POINT - ANSWER The temperature at which the vapor pressure of a liquid equals the
atmospheric pressure of 14.7 pounds per square inch (psia) or 760 mm of mercury. Where a boiling
point is unavailable for the material in question or for mixtures which do not have a constant boiling
point, for the purposes of this classification, the 20-percent evaporated point of a distillation performed
in accordance with ASTM D 86 shall be used as the boiling point of the liquid.
CEILING LIMIT - ANSWER The maximum concentration of an airborne contaminant to which one may be
exposed shall be as established by the regulations of the United States Department of Labor, as set forth
in 29 CFR Part 1910.1000, or if not listed therein, the ceiling Recommended Exposure Limit (REL-C)
concentrations published by the U.S. National Institute for Occupational Safety and Health (NIOSH), the
Threshold Limit Value — Ceiling (TLV-C) concentrations published by the American Conference of
Governmental Industrial Hygienists (ACGIH), the ceiling Workplace Environmental Exposure Level (WEEL-
Ceiling) Guides published by the American Industrial Hygiene Association (AIHA), or other approved
standard.
CHEMICAL - ANSWER An element, chemical compound or mixture of elements or compounds or both.
CHEMICAL NAME - ANSWER The scientific designation of a chemical in accordance with the
nomenclature system developed by the International Union of Pure and Applied Chemistry, the Chemical
Abstracts Service rules of nomenclature, or a name that will clearly identify a chemical for the purpose of
conducting an evaluation.
CLOSED CONTAINER - ANSWER A container sealed by means of a lid or other device capable of
preventing the escape of liquid, vapor or dusts in the ordinary course of storage, handling or use.
CONTAINER - ANSWER For solid and liquid hazardous materials, a vessel of 60 gallons or less in capacity
used for storage or transportation. For compressed gases, a cylinder, pressure vessel or tank designed for
pressures greater than one atmosphere at 68°F. Pipes, piping systems, engines and engine fuel tanks
associated with solid or liquid hazardous materials or compressed gases, shall not be deemed to be
containers if in active use.
CONTAINMENT SYSTEM - ANSWER A gas-tight recovery system comprised of devices or equipment
which, when placed over or around the portion of the compressed gas container that is leaking, stops or
controls the escape of gas from the container.
, CONTAINMENT VESSEL - ANSWER A gas-tight vessel which, when installed or placed over or around a
leaking compressed gas container, confines the container and the gas leaking there from.
CONTROL AREA - ANSWER Spaces within a building that are enclosed and bounded by exterior walls, fire
walls, fire barriers and roofs, or a combination thereof, where quantities of hazardous materials not
exceeding the maximum allowable quantities per control area are stored, handled or used, including any
dispensing.
DESIGN PRESSURE - ANSWER The maximum gauge pressure that a pressure vessel, device, component or
system is designed to withstand safely under the temperature and conditions of use.
DETACHED BUILDING - ANSWER A separate single-story building, without a basement or crawl space,
used for the storage, handling or use of hazardous materials and located an approved distance from
other buildings or structures.
DISPENSING - ANSWER The pouring or transferring by other means of any material from a container,
tank or similar vessel, which would release dusts, fumes, mists, vapors or gases to the atmosphere,
unless such release is prevented by a device, equipment or system designed for that purpose.
EXCESS FLOW CONTROL - ANSWER A fail-safe system or other approved device, equipment or system
designed to shut off flow caused by a rupture in a pressurized piping system.
EXHAUSTED ENCLOSURE - ANSWER A device, typically consisting of a hood equipped with a fan that
serves to capture and exhaust fumes, mist, vapors and gases generated at a workstation or other local
environment. An exhausted enclosure does not include a room provided with general ventilation.
EXOTHERMIC - ANSWER A process or reaction that releases energy usually in the form of heat, but also
in form of light e.g. a spark, flame, or explosion.
EXPLOSION - ANSWER An effect produced by the sudden violent expansion of gases, whether or not
accompanied by a shock wave or disruption, of enclosing materials, including the effects of chemical,
physical, and atomic sources.
