Glossary of terms

Airborne contaminants
A collective term for any type of dust, mist, vapour, gas or fume released into workroom air.
The point at which contaminants are emitted into the air is known as the source

HSG258 (Chapter 3)

Air cleaner
The part of the LEV system that removes and collects the airborne contaminant collected by the LEV system (eg a filter)

HSG258 (Chapter 7)

Air flow indicators (AIs)
Visual indicators to show the right amount of air is flowing through an LEV system (eg a manometer)


COSHH (Control of Substances Hazardous to Health Regulations)
Legislation that requires employers to control risks from exposure to hazardous substances to prevent ill health

COSHH website

An initial test of an LEV system to check it is effective at protecting workers. It is done in four stages by a competent person, usually after an LEV system has been installed or modified.

HSG258 (Chapter 8)

Combination of knowledge, skills and application experience that enables a person to do an effective and reliable job. It's the employer's responsibility to ensure staff and external suppliers are competent.

HSG 258 (Chapter 2)

The competent person who designs the LEV system, usually in response to a specification from an employer.

Information for designers

HSG 258 (Chapters 6 and 7)

Takes the airborne contaminant from the LEV hood to the discharge point, often via an air cleaner

HSG258 (Chapter 7)

The person carrying out the statutory thorough examination and test of an LEV system. Usually against data and observations obtained from the commissioning process. Person should be competent.

The amount of a hazardous substance getting into the body by inhalation, ingestion or absorption through the skin
The part of an LEV system that provides the "suck" of air to take the airborne contaminant away from the worker and through the ductwork

HSG258 (Chapter 7)

The part of an LEV system, close to the work activity, that takes the airborne contaminant away from the worker. There are three basic types.

HSG258 (Chapter 6)

The competent person that assembles the various components of an LEV system on site. They may balance the airflow through the system if there is more than one LEV hood and commission it.

HSG258 (Chapter 8)

Log Book
A book to keep a written record of regular checking, maintenance and repair of an LEV system

HSG258 (Chapter 9)

Performance checking
Routine and regular checks on an LEV system that ensure it is working properly (controlling exposure). May involve the use of airflow indicators. Should be carried out in addition to the thorough examination and test, by a competent person.

Clearing the air - INDG408

A document prepared by an LEV supplier in response to an employer's specification. It describes in detail the proposed LEV system

HSG258 (Chapter 5)

Safety Data Sheet (SDS or MSDS)
Information from your supplier that tells you about the hazards of supplied substances and how to work with them safely
The point in a process where airborne contaminants are emitted into the air

A written document describing the employer's process and where and how airborne contaminants are being generated. Preparation may require expert advice unless a suitable and effective  "off the shelf" LEV system exists. Sent to the supplier who should respond with a formal quotation.

HSG258 (Chapter 5)

Thorough examination and test
A 3-stage complete check of the LEV system, done at least every 14 months (with a few special exceptions). Often done by an external contractor. Whoever does examination should be competent. Involves a physical examination, airflow measurements and professional judgement on performance. Provides a list of prioritised remedial actions to the employer that should be acted upon.

HSG258 (Chapter 10)

User Manual
Written instructions on how to use and maintain your LEV system. Should include details of LEV system thorough examination and test

HSG 258 (Chapter 9)

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Updated 2021-01-19