Glossary

Acutely Toxic Material

A material for which the lethal exposure levels fall within the ranges shown in the table below:

Aerosols

Colloids of liquid or solid particles suspended in gas.

Biohazardous Materials

Infectious agents, the products of infectious agents, or the components of infectious agents presenting a real or potential risk of injury or illness.

Biosafety Cabinet

A ventilated cabinet which serves as a primary containment device for operations involving biohazard materials. The three classes of biosafety cabinets are described below:

Biosafety Level

Biosafety levels consist of laboratory practices and techniques, safety equipment, and a laboratory facility appropriate for the operations performed and for the hazard posed by the particular biohazard material. The Centers for Disease Control (CDC) and the National Institute of Health (NIH) define the four biosafety levels in the publication, Biosafety in Microbiological and Biomedical Laboratories, and recommend biosafety levels for particular pathogenic microorganisms.

Boiling Point

The temperature at which the vapor pressure of a liquid equals the surrounding atmospheric pressure. For purposes of defining the boiling point, atmospheric pressure shall be considered to be 14.7 psia* (760 mm Hg).

Carcinogen

(definitions from Prudent Practices in the Laboratory): Materials considered to be carcinogens include substances regulated by OSHA as carcinogenic; substances listed as “known to be a carcinogen” in the latest Annual Report on Carcinogens issued by the National Toxicology Program (U.S. DHHS, NTP); substances listed under Group 1 (“carcinogenic to humans”) by the International Agency for Research on Cancer (IARC); and other similar sources.

Class I Biosafety Cabinet

The Class I biosafety cabinet is an open-fronted negative-pressured ventilated cabinet with a minimum inward face velocity at the work opening of at least 75 feet per minute. The exhaust air from the cabinet is filtered by a HEPA filter.

Class IA Liquids

include those liquids that have flash points below 73°F (22.8°C), and boiling points below 100°F (37.8°C).

Class IB Liquids

include those liquids that have flash points below 73°F (22.8°C), and boiling points at or above 100°F (37.8°C).

Class IC Liquids

include those liquids that have flash points at or above 73°F (22.8°C), but below 100°F (37.8°C).

Class II Biosafety Cabinet

The Class II biosafety cabinet is an open-fronted, ventilated cabinet. Exhaust air is filtered with a high-efficiency particulate air (HEPA) filter. This cabinet provides HEPA-filtered downward airflow within the workspace. Class II Cabinets are further classified as Type A1, Type A2, Type B1,and Type B2 .

Class II Liquid

Any liquid that has a flash point at or above 100°F (37.8°C), and below 140°F (60°C).

Class II, Type A1 (Formerly Type A) Biosafety Cabinets

may have positive-pressure contaminated internal ducts and may exhaust HEPA-filtered air back into the laboratory. 70% of the cabinet air is recirculated and 30% is exhausted, either into the room or outside.

Class II, Type A2 (Formerly Type B3) Biosafety Cabinets

have negative-pressure ducts or plenums surrounded by negative-pressure plenums, exhaust HEPA-filtered air through external ducts to space outside the laboratory or to the environment, and have HEPA-filtered downflow air that is a portion of the mixed downflow air and inflow air from a common exhaust plenum. 70% of the cabinet air is recirculated, and 30% is externally vented. Suitable for work with minute quantities of toxic chemicals and radionuclides, if vented to the environment.

Class II, Type B1 Biosafety Cabinets

exhaust HEPA filtered air through external ducts to space outside the laboratory, and have HEPA-filtered downflow air. Thirty percent of the cabinet air is recirculated, and 70% is externally vented. Suitable for work with minute quantities of toxic chemicals and radionuclides.

Class II, Type B2 Biosafety Cabinets

exhaust HEPA-filtered air through external ducts to space outside the laboratory, and have HEPA-filtered air downflow air drawn in from the laboratory or outside air. One hundred percent of the cabinet air is externally vented without recirculation. Suitable for work with minute quantities of toxic chemicals and radionuclides.

Class III Biosafety Cabinet

The Class III biosafety cabinet is a totally enclosed, negative-pressure ventilated cabinet of gas-tight construction. Operations within the Class III cabinet are conducted through protective gloves. Supply air is drawn into the cabinet through high-efficiency particulate air filters. Exhaust air is filtered by two high-efficiency particulate air filters placed in series, or by high-efficiency particulate air filtration and incineration, and discharged to the outdoor environment without recirculation.

Class IIIA Liquid

Any liquid that has a flash point at or above 140°F (60°C), but below 200°F (93°C).

Class IIIB Liquid

Any liquid that has a flash point at or above 200°F (93°C).

Combination Unit

An interconnected assembly of an eyewash and safety shower, supplied by a single plumbed source.

Combustible Liquid

A combustible liquid shall be defined as any liquid that has a closed-cup flash point at or above 100°F (37.8°C).

Compressed Gas

A gas or mixture of gases having an absolute pressure exceeding 40 psi at 70°F (21°C) in a container; a gas or mixture of gases having an absolute pressure exceeding 104 psi in a container at 130°F (54°C), regardless of the pressure at 70°F (21°C), or both; or a liquid having a vapor pressure exceeding 40 psi at 100°F (38°C) as determined by UFC Standard No. 9-5.

Containment

The combination of personal practices, procedures, safety equipment, laboratory design, and engineering features to minimize the exposure of workers to hazardous or potentially hazardous agents.

Cryogenic Fluids (“Cryogens”)

Elements and compounds that vaporize at temperatures well below room temperature. Most common cryogens have a normal boiling point below approximately 120 K. Helium-4 (4.2 K), hydrogen (20 K), nitrogen (77 K), oxygen (90 K), and methane (112 K) [normal boiling point temperatures in parentheses] are examples of cryogens.

Decontamination

Removal or destruction of infectious agents; removal or neutralization of toxic agents.

Emergency Shower or Deluge Shower

A unit consisting of a shower head controlled by a stay-open valve that enables a user to have water cascading over the entire body.

Eyewash

A device used to irrigate and flush the eyes.

Flammable Anesthetic Gas

A compressed gas that is flammable and administered as an anesthetic including cyclopropane, divinyl ether, ethyl chloride, ethyl ether, and ethylene.

Flammable Liquid

Any liquid that has a closed-cup flash point below 100°F (37.8°C). Class I Liquid: Any liquid that has a closed-cup flash point below 100°F (37.8°C) and a Reid vapor pressure not exceeding 40 psia at 100°F (37.8°C).

Flash Point

The minimum temperature of a liquid at which sufficient vapor is given off to form an ignitable mixture with air, near the surface of the liquid, or within the vessel used.

Fume Hood

A device enclosed on three sides, as well as the top and bottom, with an adjustable sash or fixed partial enclosure on the remaining side. They are designed, constructed, and maintained so as to draw air inward by means of mechanical ventilation, and so that any operation involving hazardous materials within the enclosure does not require the insertion of any portion of a person's body other than the hands and arms into the work area. (Note: Laboratory fume hoods prevent toxic, flammable, or noxious vapors from entering the laboratory; present a physical barrier from chemical reactions; and serve to contain accidental spills).

Highly Toxic Material

Material that produces a lethal dose or lethal concentration that falls within any of the following categories:

  • A chemical that has a median lethal dose (LD50) of 50 milligrams or less per kilogram of body mass (mg/kg) when administered orally to albino rats of between 200 and 300 grams each.
  • A chemical that has a median LD50 of 200 mg/kg when administered by continuous contact with the bare skin of albino rabbits of between 2 and 3 kilograms each for 24 hours, or less if death occurs within 24 hours.
  • A chemical that has a median lethal concentration (LC50) in air of 200 parts per million by volume or less of gas or vapor, or 2 milligrams per liter or less of mist, fume, or dust, when administered by continuous inhalation for one hour, or less if death occurs within one hour, to albino rats between 200 and 300 grams each.

NOTE: Mixtures of these materials with ordinary materials, such as water, may result in an unwarranted classification of a material as highly toxic. While this system is basically simple in application, any hazard evaluation that is required for the precise categorization of this type of material shall be performed by experienced, technically competent persons.

HIV/HBV Research Facility

A laboratory producing or using research-laboratory scale amounts of HIV or HBV. Research laboratories may produce high concentrations of HIV or HBV, but not in the volume found in production facilities.

Laser Hazard Class

The relative hazard of a given laser or laser system as specified in the ANSI Z136.1 Standard. Present laser Classes are 1, 2, 3a, 3b, and 4. Generally, only Class 3b and 4 lasers present hazards sufficient to require specialty laboratory designs.

Local Exhaust Ventilation

Exhaust applied close to a source of air contaminants to prevent the migration of those contaminants into the breathing zones of people. It is often used for control of exposures to hazardous chemicals when the apparatus is not appropriate for placing in a fume hood. These applications shall be evaluated by EH&S for exposure control, and possible impacts on other ventilation systems.

Maximum Permissible Exposure (MPE)

The level of any radiation to which a person may be exposed without hazardous effect or adverse biological changes in the organ(s) of concern. The MPE is normally expressed at a specific energy/frequency/wavelength and a defined exposure duration.

Microwave Radiation

That portion of radiofrequency energy consisting of radiation with frequencies between 300 GHz and 300 MHz.

Non-Ionizing Radiation (NIR)

All electromagnetic radiation with photon energy less than 12.4 eV (> 100 nm wavelength) and electric or magnetic fields. Examples are: Lasers, nuclear magnetic resonance (NMR), microwave devices, radio-frequency devices, high-intensity ultraviolet (UV) and infrared sources, and high-powered magnets. It is usually assumed that energy at frequencies below 300 MHz exists as discrete electric and magnetic fields rather than as electromagnetic radiation.

Nonflammable Medical Gas

A compressed gas, such as oxygen or nitrous oxide, which is nonflammable, but a strong oxidizer, and used for therapeutic purposes.

Operational Volumetric Flow Rate

The volumetric flow rate of supply air ventilation delivered to meet the minimum airflow requirements of a laboratory space for the comfort of the typical number of occupants, plus sufficient volume to maintain negative pressurization of the space. The exhaust volumetric flow rate will be variable in labs equipped with variable air volume (VAV) hoods.

Optical Radiation

Any radiation whose wavelength is between 100 nm and 1 mm. Lasers normally fall into this area.

Power-Frequency Field

Any field whose frequency is between 3 kHz and 1 Hz.

Pressure Vessel

Storage tank or vessel that has been designed to operate at pressures above 15 psig.

Radio Frequency Energy (Radiation)

Any energy with frequencies in the range between 3 kHz and 300 GHz.

Static Magnetic Fields

Direct current (zero Hz) magnetic fields. Magnetic flux density (often called magnetic field strength) is expressed in A/m, Gauss (G), or Tesla (T). The units are related as 1 A/m = 12.6 mG = 1.26 μT.

Tepid Water

Water which is moderately warm or lukewarm.

Threshold Limit Value/Ceiling (TLV-C)

The exposure limit that should not be exceeded, even for an instant.

Threshold Limit Value/Time Weighted Average (TLV-TWA)

The time weighted average exposure allowed for an 8-hour workday and a 40-hour workweek.

Toxic Material

Classes of toxicity include “acutely” and “chronically toxic.” Included within the class of materials that exhibit chronic toxicity are carcinogens, mutagens, and teratogens.

Toxic Material

A material that produces a lethal dose or a lethal concentration within any of the following categories:

  • A chemical or substance that has a median lethal dose (LD50) of more than 50 milligrams but not more than 500 milligrams per kilogram of body weight when administered orally to albino rats of between 200 and 300 grams each.
  • A chemical or substance that has a median lethal dose (LD50) of more than 200 milligrams but not more than 1,000 milligrams per kilogram of body weight when administered by continuous contact with the bare skin of albino rabbits of between 2 and 3 kilograms each for 24 hours, or less if death occurs within 24 hours.
  • A chemical or substance that has a median lethal concentration (LC50) in air more than 200 parts per million but not more than 2,000 parts per million by volume of gas or vapor, or more than two milligrams per liter but not more than 20 milligrams per liter of mist, fume, or dust, when administered by continuous inhalation for one hour, or less

Vapor Pressure

The pressure, often measured in psia, exerted by a liquid.