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Chasing saws and carbon monoxide

Medical studies have shown that exposure to excess carbon monoxide can lead to a variety of serious health effects. Operators of petrol powered chasing saws working inside buildings are particularly at risk. Chasing saws are used during building or renovation projects to cut channels in brick or concrete.

WorkSafe Scientific Inspectors have conducted extensive risk assessment testing of hand held petrol powered brick and concrete chasing saws. These tests have clearly demonstrated that carbon monoxide exposures, when using these saws, are well in excess of the legal Occupational Exposure Standards, including in situations where chasing is done prior to the installation of the roof.

Contents

  1. What is carbon monoxide?
  2. Who may be exposed?
  3. Dangerous levels may be reached within one minute
  4. Other hazards
  5. Risk assessment
  6. Operator options
  7. WorkSafe to take action
  8. More information

What is carbon monoxide?

Carbon monoxide is a colourless, odourless gas which makes it difficult to detect. If inhaled it can have serious short and long-term health effects.

The warning signs of exposure to low concentrations of carbon monoxide include headaches, a tight forehead, flushing, nausea and reduced fine motor skills. Exposure to high concentrations of carbon monoxide can quickly lead to severe headaches, vomiting, weakness, coma, convulsions and possibly death.

Short-term effects of carbon monoxide include drowsiness, headaches, irritability, decreased judgement, reduced motor skills and convulsions. In the long term, carbon monoxide affects the heart, circulation and nervous system. It damages blood vessels and can aggravate existing cardiovascular conditions.

Who may be exposed?

Workers using petrol, LPG/LNG or diesel motors are likely to be exposed to carbon monoxide. Two stroke petrol engines produce more carbon monoxide gas than other types of motor. WorkSafe Scientific Inspectors have identified workers using petrol powered chasing saws as being particularly at risk. Exposure to carbon monoxide while using petrol powered chasing saws is also a concern because of the additional hazards that workers face.

Dangerous levels may be reached within one minute

The Australian Standard for occupational exposure is an average of 30 parts per million (ppm) in air over an eight hour period. Levels should never exceed 400ppm at any one time. However, investigations by Inspectors have shown that where a petrol powered chasing saw is used in an enclosed space, levels can reach 1000ppm within one minute. Even in a house with an open roof, levels can reach 400ppm within between 6 and 30 minutes, depending on wind strength. Workers generally work on several houses per day, frequently working on each house for 30 minutes or more. This means that the accumulated effect of the carbon monoxide inhaled during a normal workday places users of petrol powered chasing saws well above the levels given in the ‘Exposure Standards for Atmospheric Contaminants in the Occupational Environment [NOHSC:1003(1995)’.

Other hazards

Chasing saw users can be exposed to other hazards. The saws create sulphur dioxide and other hazardous fumes, as well as silica quartz dust, which can be inhaled if dust controls are not adequate. The blade is also clearly a hazard. The saws create a slurry – a mixture of brick or concrete and water, which is a slip hazard. PPE is required because noise levels can permanently damage hearing, and particles can flick into the eyes. Because the saw is heavy, and is often used at awkward angles, there is a manual handling hazard. Vibration is a concern, however, adequate breaks, appropriate gloves and equipment can reduce this. Because these workers sometimes work alone, they should have a means of communication with others, to prevent incidents occurring without someone being aware.

Risk assessment

It is important to identify workers who may be at risk of carbon monoxide exposure. Any worker that inhales fumes from fuel-powered machinery is at risk. This includes workers using, or working near, cars, petrol powered chain saws, forklifts or generators indoors.

Operator options

If petrol powered chasing saws are used indoors (including where the roof has yet to be installed) then the fumes must be exhausted safely to the out side of the building or structure via a local exhaust hose. Other safe alternative chasing systems may be used and these may include, but are not limited to: hydraulic or pneumatic systems or the use of an electric-grinder vac system where the operator wears a dust mask or respirator that complies with Australian Standard AS1716 to prevent inhalation of crystalline silica.

Where possible, chasing saws should be used in new houses before the roof is constructed. While this, along with opening doors and windows and using fans can reduce the amount of carbon monoxide in the air, it is inadequate as a control as levels can still rise above the standard. Carbon monoxide can accumulate surprisingly quickly even in areas that appear to be well-ventilated – sometimes resulting in dangerous and potentially fatal concentrations.

WorkSafe to take action

Although the carbon monoxide exposure standards and other applicable regulations (for example, regulation 5.20) have been in Part 5 of the Occupational safety and Health Regulations since 1996, operator compliance has been minimal.

WorkSafe inspectors are likely to enforce this matter via Improvement and Prohibition Notices along with possible prosecution where the circumstances meet WorkSafe’s Enforcement Policy,  this may include where operators knowingly continue to use petrol powered chasing saws without fume extraction.

More information

Further information can be found in the following, or by telephoning WorkSafe on 9327 8777.

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