Paint stripping using methylene chloride in a tank
Methylene chloride is a volatile solvent used to strip paint from timber. Exposure can cause serious injury or even death.
What is methylene chloride?
Methylene chloride is a volatile solvent used to strip paint from timber. It is also referred to as dichloromethane.
How is methylene chloride used in the paint stripping industry?
Paint stripping typically involves immersing an item in methylene chloride in an open tank, leaving it to soak for several hours or overnight and then washing it off using high-pressure water. Manual scrubbing and scraping is often carried out to remove excess paint after soaking. When dealing with large and bulky timber furniture which can only be partially immersed, employees scoop and pour methylene chloride over the item and then scrub it with a brush while it is in the tank.
What are the dangers?
Inhalation of high levels of methylene chloride vapour can cause death.
Inhalation of methylene chloride can also cause:
irritation to the respiratory tract and eyes
central nervous system depression which can lead to unconsciousness and death
When skin comes into contact with the liquid it can result in dry skin, dermatitis and severe chemical burns.
Methylene chloride is assigned as a Category 2 suspected human carcinogen under the Globally Harmonised System for the Classification and Labelling of Chemicals (GHS). This means that it may be a carcinogen in humans but the evidence is not sufficient.
Due to this GHS classification, methylene chloride is considered to be as a hazardous substance under the Occupational Health and Safety Regulations 2017.
What are employers' legal duties?
Employers who use hazardous substances such as methylene chloride have legal duties under the Hazardous Substances Part of the Occupational Health and Safety Regulations 2017 (OHS Regulations).
The Victorian Compliance Code for Hazardous Substances (2018) provides practical guidance on how to comply with the OHS Regulations.
get the current safety data sheets (SDS) for methylene chloride and ensure that they are accessible to employees that use it or may be exposed to it. Employers may make the SDS accessible in languages other than English. They must also ensure that information in the SDS is not altered
set up a hazardous substances register which includes a list of the product names of the chemicals used and a copy of each SDS, and make this readily accessible to employees who may be exposed to the hazardous substance
legibly label containers, drums and tanks accordance with the OHS Regulations including:
the product identifier of the hazardous substance
manufacturer's or importing supplier's label
control the risks associated with the use of methylene chloride
ensure that exposure of employees does not exceed the national 8 hour average exposure standard of 50ppm (parts per million) in air
provide information, instruction and training on how to handle and use methylene chloride safely
conduct air monitoring if they are uncertain about employees’ exposure, or if it is needed to determine if there is a risk to health. Results must be provided to any employee who has or may have been exposed to a hazardous substance. A record of the results must be kept for 30 years
provide supervision to ensure employees work in a safe manner and use the control measures provided
make sure that control measures (respirators, work practices, ventilation) are being properly used and maintained
Employers who don’t comply with their legal duties may face penalties.
The employer needs to consult with employees and any health and safety representative in the workplace when assessing and controlling risks.
How can you control or minimise the risks?
An employer should use the hierarchy of control in the workplace. It ranks methods of controlling risks from the highest and most effective level of protection to the lowest and least effective.
Eliminating the risk is the highest level of control, followed by reducing the risk through substitution, isolation and engineering controls, then reducing remaining risk through administrative controls. Reducing the risk through the use of protective personal equipment is the lowest level of control.
Ways of controlling or minimising the risks of working with methylene chloride are explained below.
Eliminate or substitute the use of methylene chloride
Don't use methylene chloride if you don't have to.
Use a less hazardous product or a different method of stripping paint. For example, use a mechanical method such as sanding, water-based products or a brush-on paste rather than liquid methylene chloride to minimise vapours.
Eliminate the headspace or the need to lean into the tank
The headspace is the space above the level of the liquid and the top of the tank. Extremely high levels of vapour build up in the headspace of a tank and inhalation can lead to death. Therefore fatalities can be prevented by either eliminating the headspace or the need to lean into the headspace. This can be achieved by the following methods.
Raising the tank height
By raising the tank off the floor, employees wearing respirators can work upright without the need to lean over and into the tank. This may reduce the risk further.
Using tailor made tanks of different sizes and shapes to suit items handled
For example, large deep tanks should be used for items such as wardrobes or dressers, long narrow shallow tanks can be used for skirting boards and long skinny deep tanks can be used for doors. This requires less solvent and reduces employee exposure by minimising the surface area of the solvent and the space in which vapours can accumulate.
Increasing the depth of solvent close to the top of the tank
This practice not only eliminates the headspace in the tank but also allows the items to be fully immersed and left to soak. The need to manually pour solvent over a partially immersed item and scrub is eliminated or reduced.
Conducting manual tasks outside of the tank
Where practicable, conduct manual tasks such as scrubbing and scraping away from the tank. If the paint has not been completely removed, it can be placed back into the tank to soak for longer.
Use mechanical lifting devices to manoeuvre items
Mechanical lifting devices such as small hoists (often roof mounted) allow the operators to distance themselves from vapours and any splashes that may occur when moving items. The use of such devices also eliminates or reduces the need to lean into the tank to move items.
Wear an airline respirator
The vapour levels of methylene chloride in the headspace of a partially filled tank are extremely high and can lead to death. If there is a likelihood that an employee may lean into the headspace of the tank to retrieve or scrub an item, then they should wear an air-supplied respirator.
Organic vapour cartridge respirators are generally not suitable for prolonged exposure to such high levels of methylene chloride as the vapour can readily break through the charcoal filter.
Ensuring employees do not work alone
Employees should not work alone when stripping paint with methylene chloride, particularly if they are likely to lean into the tank.
Other ways to minimise exposure to methylene chloride
Exposure to methylene chloride can be also minimised by:
ensuring there is good general ventilation by keeping doors and windows open
placing covers over tanks when they are not in use
adding a layer of water, wax or suitable medium such as wooden balls to the surface of the solvent to reduce evaporation and the build-up of vapour in the tank
reducing the duration of workers’ exposure to methylene chloride by rotating them through various tasks in the workplace
Local exhaust ventilation, such as extraction fans or hoods over or next to the tank, may reduce general exposure. However they are not considered an effective solution when employees need to lean into the tank as the vapours are drawn up towards their face.