Safety Tips

Gas Detection


What do you know about hazardous atmospheres? If you're doing gas tests, you need to know all about gases and hazardous atmospheres.

Different gases have a variety of characteristics - some are heavier than air, others are lighter than air. Some gases have a colour, others are invisible. Some have a distinct odour, many do not. Different processes produce different hazardous atmospheres. If you don't know what to look for, you probably won't find it. And "it" may be deadly.


If you don't follow correct gas detecting procedures, you could get false readings and let your co-workers enter an unsafe area. They could:

Suffer permanent disabilities and/or brain damage

Exposure Limits

Exposure limits are measurements that describe the concentration levels of gases a person can be exposed to for a certain amount of time without adverse health effects. These include:

8-Hour Contamination Limit - concentration of gas which most workers can be exposed to day after day without adverse effects
15-Minute or Ceiling Contamination Limit- the maximum concentration workers can be exposed to for a 15 minute maximum of time or a one-time exposure on a daily basis

For additional information on exposure limits, refer to current OHS Legislation.

Air Currents

Assessing the direction and strength of air currents is an important step in gas testing. Your air quality testing kit should contain air current tubes. These tubes generate a flow of distinct, white, lighter-than-air smoke that helps you to determine the direction and velocity of the air current.


There are many types of gas testers available. Each have specific applications. You need to know what type you need for your work site. If you don't use the right equipment, you could miss detecting a deadly atmosphere.


Take a good look at your equipment before you use it. Problems with equipment can lead to disaster. Be sure to:

Look for signs of wear or cracks
Check that nuts, screws, and screw joints are firmly connected
Look for cracks or wear in the rubber seams on the bellows pump
Test the bellows pump for air leaks. Fully squeeze the pump and insert a detector tub in the inlet hole. If there is a leak, you will notice a loss of air in the bellows


Before testing, think about the entire process:

What work place conditions exist that might affect the testing?
What substances are you testing for? Does your test include ALL possibilities?
Do you have the gas detector tube instruction sheets for the gas you are testing for? Do you understand them all?
What are the properties of the substances you are testing for?
When are you going to complete the tests?
How often do tests need to be done in each area?


When you are testing:

Evaluate the air quality using gas detection procedures specific to your equipment
Follow specified sampling times
Observe tube colour changes as outlined on the detector tube instruction sheet
Keep accurate records of all tests including the exact location, time of testing, and results
Record results immediately after testing
Wear the correct personal protective equipment (PPE)
Follow safe work procedures
Keep other factors in mind during testing - temperature, humidity, atmospheric pressure, presence of other gases or vapours
Purge the gas detector with clean air following each air sample test (draw air through the instrument several times)

Gases in the Home

Homes are not immune to hazardous atmosphere. In fact, we use chemicals and processes everyday that are potentially dangerous. Some products often found in homes are:

Aerosol cleansers
Household paints
Natural gas
Garden weed control products

Most chemical products you buy for use in your home will outline specific safety steps.

Sometimes natural gas can exist at high levels within your home. Obviously, you need to know if conditions in your home are hazardous.

Some less expensive gas testers may be affordable for home use. But many of these testers may not test for the necessary substances. As well, people who do gas testing on the work site are trained professionals-this is nothing to fool around with.

If you suspect a hazardous atmosphere in your home or garage, get a professional to check it out.

You Can Save Lives

Most accidents in hazardous atmospheres happen because workers don't know that the atmosphere is dangerous. These accidents are usually preventable. By careful initial and on-going gas testing with the right equipment, you can stop incidents before they happen.

For more information, refer to current applicable Occupational Health and Safety Legislation.