Topics explained – Airborne contaminants

The atmosphere around you at work may be hazardous; however, this is often difficult to detect as airborne substances may be odourless or colourless.

Workers may be exposed to a variety of airborne substances such as:

  • dusts
  • fumes
  • gases
  • vapours
  • mists
  • smoke.

Vehicle emissions within automotive shops, particularly of diesel, are a serious problem, as are welding and paint fumes.

It’s important to keep concentrations of all airborne contaminants as low as possible, regardless of if they are known to present a health hazard. Dusts and fumes can also accumulate or remain suspended in the air for long periods of time.

Cleaning up dusts can actually worsen the problem as smaller particles can be transported from the initial exposure/emission point to another through air, wind or on clothing.

Monitoring contaminants

PCBUs are responsible for ensuring that workers are not exposed to contaminants above the workplace exposure standards. This standard relates to a particular chemical or substance within a worker’s breathing zone that could cause dangerous health effects or undue discomfort. The legal concentration limits for a particular chemical or substance must be adhered to.

You should consider monitoring contaminant levels for chemicals with exposure standards:

  • if there is uncertainty about whether the exposure standard has been or may be exceeded, or
  • to determine whether there is a health risk.

Using monitoring equipment, an atmosphere is considered dangerous if the results indicate:

  • an unsafe oxygen level, which is common to grain silos and waste pits
  • a concentration of oxygen resulting in increased risk of fire
  • a concentration of flammable gas, vapour, a mist of fumes exceeding 5% or the lower explosive limit
  • a presence of combustible dust, such as wood dust, bio-solids, sugar, starch, flour, feed or grain in a quantity and form that would result in a hazardous area. Dust explosions usually occur when combustible dust or fibre from paper, grain, organic compounds and meals accumulates, is disturbed and released into the air, and ultimately comes into contact with an ignition source.

Records of air monitoring for airborne contaminants must be kept for a minimum of 30 years, and are required to be available to workers who are exposed.

Safe Work Australia is reviewing the Workplace exposure standards for airborne contaminants and releasing the draft evaluation reports and recommendations on their website.

Safety solutions

To maintain a safe working environment for everyone:

  • regularly inspect and clean ventilation and dust collection systems to remove dust build-up
  • isolate the hazard by either enclosing processes or using a remote operation, such as pendant controls, enclosed vehicle cabs and control rooms
  • install local exhaust ventilation to capture dust and fumes at the source
  • provide personal protective equipment (PPE) that is:
    • suitable for the nature of the work and the hazard, such as gloves, masks, goggles, face shields and respirators
    • comfortable to wear, and of a suitable size and fit
    • maintained, repaired or replaced when required
    • used or worn by workers who have been trained in its use and care
  • adopt good workplace hygiene practices, like having a regular cleaning routine where you vacuum or wet mop the floors instead of sweeping them
  • consider your lunch rooms and/or non-work areas as clean zones, where contaminated PPE must be removed before entering.

Local exhaust ventilation systems

Local exhaust ventilation (LEV) systems provide a positive means of removing airborne contaminants from the working environment by capturing them at their source.

Such systems are required when worker exposure to airborne emissions is not satisfactorily controlled by general dilution ventilation. Factors contributing to the need for LEV include:

  • contaminants which are relatively hazardous
  • high emission levels which are likely to need excessive volumes of air to control airborne concentrations using dilution ventilation
  • location of workers in the immediate vicinity of the emission
  • emissions that are intermittent or emission rates which vary with time
  • extended duration of potential worker exposure to emissions, making the less desirable alternative of relying on personal protective equipment (PPE) unacceptable due to discomfort and cost of consumables
  • emission sources that are relatively fixed, rather than mobile
  • legislation requiring exhaust ventilation.

Local exhaust ventilation systems must be carefully designed to ensure they:

  • effectively remove the dust or fume
  • do not alter or interfere with the work process
  • do not increase the lead exposure to other workers (for example, by exhausting the fume or dust to other work areas)
  • do not increase the exposure to the worker by pulling the fume past the worker’s breathing area.

The effectiveness and efficiency of LEV systems varies depending on design parameters. Engineering expertise with specialised knowledge is usually necessary to achieve the optimal design for effective and economical operation.


To design an LEV system, the supplier will need to know:

  • the key properties of the airborne contaminants, to determine capture velocity required
  • how the dust, gas or mist is generated (eg the source), which may also affect capture velocity
  • the needs of workers performing tasks near the sources (capture away from workers breathing zone)
  • how much control is required
    • what is the allowable exposure limit, if any?
    • are any other controls implemented?
    • what is the exposure duration?
  • future preventative maintenance requirements and keeping inspection records.

The process should be enclosed as much as possible. Where an enclosed design cannot be used, an efficient flange should be incorporated. The hood should be located as close as practicable to the process and not draw contaminated air through the breathing zone of the worker, which is a frequent problem with canopy hoods.

The type and specification of filtration and collection equipment will depend on various factors relating to the containment, the process and environmental considerations.

Ventilation systems which recirculate filtered air back into the workplace atmosphere must be designed to be capable of capturing all hazardous contaminants.

Ducts should be as short and straight as possible. If bends or changes in diameter are necessary, they should be gradual to minimise resistance to airflow.

Extracted air must be released to a safe place and not create another hazard. If discharged outside the building, Environment Protection Authority requirements should be considered.

Appropriate cleaning and maintenance procedures must be devised and strictly implemented.

Further information