• A


    Action Level: A concentration (calculated as an 8-hour TWA) that triggers OSHA’s exposure monitoring and/or medical surveillance requirements.


    American Conference of Governmental Industrial Hygienists

  • B


    Joining two or more pieces of metal by melting a filler metal into the joint.

  • C

  • D


    A unit used to measure the intensity of a sound by comparing it with a given level on a logarithmic scale. All decibel measurements in this database are A-weighted (dBA).

    Data Source: Jobsite

    This option retrieves measurements that were gathered on an active construction jobsite during normal production and work processes.

    Data Source: Lab/Experimental

    This option retrieves measurements that were gathered in a laboratory or an experimental setting.

  • E

    8-hour TWA

    The average concentration of a hazardous substance over an 8-hour period. It is calculated as: 8-hour TWA = (concentration x task duration) / 8 hours.


    An engineering control that protects the worker from a hazardous substance by isolating them in a closed cab that provides filtered, climate-controlled air.

  • F

  • G

    Geometric Mean

    The geometric mean is a type of mean or average, which indicates the central tendency or typical value of a set of numbers by using the product of their values, as opposed to the arithmetic mean which uses their sum. The geometric mean is defined as the nth root of the product of n numbers, i.e., for a set of numbers x1, x2...xn.

  • H

  • I

  • J

  • K

  • L

    Local exhaust ventilation (LEV)

    An engineering control that reduces worker exposure to airborne contaminants by capturing emissions at the source and transporting them to a filter or safe emission point.

  • M


    µg = micrograms

    MIG-Metal Inert Gas Welding

    Also known as gas metal arc welding (GMAW).

  • N


    National Institute for Occupational Safety and Health

  • O


    Occupational Safety and Health Administration

  • P


    Permissible Exposure Level: The maximum concentration of a hazardous substance that a worker may be legally exposed to under OSHA regulations.

  • Q

  • R


    Recommended Exposure Limit: An occupational exposure limit that has been recommended by NIOSH for adoption as an OSHA PEL.

  • S


    Partially enclosed, e.g. two walls.

    SMA-Shielded Metal Arc Welding

    Also known as manual metal arc welding (MMAW) or stick welding.

  • T


    Time-Weighted Average: An average concentration of a hazardous substance over a given period of time.


    Threshold Limit Value: A concentration of a hazardous substance which a worker can be exposed to day after day for a working lifetime without adverse health effects, according to ACGIH.

  • U

  • V

  • W

    Weathering steel (588)

    Also known as COR-TEN steel.

    Wet method

    An engineering control that uses a water stream or spray to control dust emissions at the source of generation. Also referred to as water suppression.

  • X

  • Y

  • Z