Action level. An airborne concentration of benzene of 0.5 parts per million (ppm) calculated as an eight-hour time-weighted average.

Authorized personnel. Individuals specifically permitted by the employer to enter the exposure control area to perform necessary duties, or to observe employee exposure evaluations as a designated representative.

Benzene. Liquid benzene, benzene vapor, and benzene in liquid mixtures and the vapors released by these liquids.

The chemical abstract service (CAS) registry number for benzene is 71-43-2. CAS numbers are internationally recognized and used on safety data sheets (SDSs) and other documents to identify substances. For more information, see http://www.cas.org/about.

Breathing zone. The space around and in front of an employee's nose and mouth, forming a hemisphere with a 6- to 9-inch radius.

Bulk wholesale storage facility. Any bulk terminal or bulk plant where fuel is stored before its delivery to wholesale customers.

Container. Any container, except for pipes or piping systems, that contains benzene. It can be any of the following:

• Barrel;

• Bottle;

• Can;

• Cylinder;

• Drum;

• Reaction vessel;

• Storage tank.

Day. Any part of a calendar day.

Designated representative. Any of the following:

• Any individual or organization to which an employee gives written authorization;

• A recognized or certified collective bargaining agent without regard to written employee authorization; OR

• The legal representative of a deceased or legally incapacitated employee.

Emergency. Any event that could or does result in the unexpected significant release of benzene. Examples of emergencies include equipment failure, container rupture, or control equipment failure.

Exposure. The contact an employee has with benzene, whether or not protection is provided by respirators or other personal protective equipment (PPE). Contact can occur through various routes of entry such as inhalation, ingestion, skin contact, or skin absorption.

Licensed health care professional (LHCP). An individual whose legally permitted scope of practice allows him or her to provide some or all of the health care services required for medical evaluations.

Permissible exposure limits (PELs). PELs are employee exposures to toxic substances or harmful physical agents that must not be exceeded. PELs are also specified in various WISHA rules found in other chapters. The PELs for benzene are the:

• Eight-hour time-weighted average (TWA8) of 1 part per million (ppm); AND

• Fifteen-minute short-term exposure limit (STEL) of 5 ppm.

Short-term exposure limit (STEL). An exposure limit averaged over a fifteen-minute period that must not be exceeded during any part of an employee's workday.

Time-weighted average (TWA8). An exposure limit averaged over an eight-hour period that must not be exceeded during an employee's workday.

Vapor control systems. Equipment that controls the vapor displaced when chemicals are loaded and unloaded from truck or storage tanks. It also processes or balances the vapor back into the truck or storage tanks.