MRO Magazine

Dangers of compressed air include explosion; Both bosses and workers are responsible for health and safety.

The results of a recent survey conducted among maintenance, operations and engineering personnel in Canadian factories identified that the plant safety issue is the most interesting topic for people t...

December 1, 2002
By Simon Fridlyand, P.Eng

The results of a recent survey conducted among maintenance, operations and engineering personnel in Canadian factories identified that the plant safety issue is the most interesting topic for people to read about in trade magazines. That’s not surprising, since we all want to work in a safe environment. We want to come home after a good day’s work. We don’t want to have any long- or short-term health effects related to our occupational exposure.

We, as a society, have certain expectations of our work places. Our provincial governments are enforcing standards on our behalf. Government inspectors, however, cannot be everywhere all the time. As a result, a system of internal responsibilities has been implemented.

Under this system, all those involved in manufacturing activities are responsible for making sure that we have a healthy and safe environment. There are particular responsibilities for owners, employers and workers. These responsibilities lead to liabilities — both corporate and personal.

That’s why this column, The Safety File, has been created — to address numerous health and safety issues affecting industrial establishments. It will discuss a practical approach to health and safety.

In my daily work at S.A.F.E. Engineering in Toronto, I am faced with finding engineering solutions to many health and safety issues.

I believe factories can be made safe through solid engineering, guided by the following principles:

a) Whatever is recommended has to be acceptable to the end user. The people who operate the equipment must have a say in safety issues.

b) There should be no impact on productivity, so production is not affected, and

c) Recommendations must be in compliance with acceptable codes and standards.

Compliance to codes and standards represents the best engineering practice. It is quite achievable to have a safe and productive workplace. As you know, safety is directly related to productivity. It pays to invest in safety. So let’s begin with our first subject of concern.

Compressed air dangers

Today’s topic is compressed air. On many occasions I have noticed that compressed air is used to blow dust from machinery or clothing worn by workers — for example, in woodworking shops, or where paint or adhesive is applied to a surface.

There are specific requirements for compressed air listed in the Occupational Health Act and Fire Codes: “Compressed air or other compressed gases shall not be used to blow dust from surfaces inside buildings.” The reason for this is not be what you might think. The requirement is because combustible dust, when in suspension, may be ignited by static electricity generated by the compressed air.

The practical solution would be to use a dust collection system to get rid of the dust, instead of blowing it from one place to another. Housekeepers understood this principle a long time ago.

Ontario’s Occupational Health and Safety Act states that compressed air shall not be used for blowing dust from clothing worn by workers, except where the device itself can limit an increase in pressure when the nozzle is blocked. A simple pressure regulator could be used as such a device.

The requirement is obvious when you consider that if the nozzle is blocked, the buildup of pressure could cause the hose to rupture. This situation may injure a worker. The practical approach would be to use a vacuum cleaner to remove the dust or have a pressure-limiting device installed on the air line.

The use of direct compressed air to spray flammable paints, lacquers and adhesives is also prohibited for the same reason. A chance of explosion exists in this situation. I have seen situations where a compressed air hose is directly attached to the paint canister, so the compressed air is actually pushing the paint out of the canister.

For an explosion to take place, three ingredients are required. They are: a) air fuel mixture (obviously, pushing compressed air into a canister creates a very good mixture), b) confinement (the shell of the canister), and c) a source of ignition (a spark created by static electricity, which is present in compressed air).

As you can see, all of the ingredients for an explosion occur in this situation.

The best practice is to use a double diaphragm pump that is operated by compressed air to spray the paint. When a pump is used, there is no direct connection between the compressed air and the flammable liquid. It’s that simple.

Health and safety is everyone’s business. We cannot afford to have accidents that result in human and financial costs. As with the use of compressed air, an understanding of the issues and proper engineering provides the answers.

Safety File columnist Simon Fridlyand, P.Eng., is president of S.A.F.E. Engineering of Toronto, a company specializing in Pre-Start Health and Safety Reviews and audits for fire code compliance. He can be reached at 416-447-9757.