Many industrial sites contain vast quantities of flammable and toxic materials. In order to ensure the health and safety of all employees, contractors, and the public at large, determinations must be made as to whether any of these materials may be present and the quantities of each.
Knowledge is one of the key ingredients in developing safe work practices. The ability to test and monitor the atmosphere for any hazardous concentrations is a critical component to any organization’s safety management system.
Gas testing and atmospheric monitoring are often viewed as the same activity. However, this is not the case as each term actually refers to a very different activity. Gas testing is a task where measurements are taken for a specific hazard or group of hazards in a specific location. It is typically performed prior to beginning a task and the results will dictate what control measures need to be taken to ensure the health and safety of the employees.
Atmospheric monitoring is an activity where the general work atmosphere is continually measured to ensure that there are no changes in the area during the task. Monitoring is typically completed as a result of the gas testing.
When performing atmospheric testing and/or monitoring, there are typically three key items to measure in the atmosphere:
- Oxygen content
- Presence and amount of flammable gasses
- Presence and amount of toxic gasses
Gas detection equipment is for use by trained and qualified personnel. It is designed to be used when performing a hazard assessment to assess potential worker exposure to oxygen deficiency or enrichment, as well as combustible and toxic gases and vapours. Training on the actual use, maintenance, limitations, and proper selection of this equipment is critical. More than one type of gas can give the same or similar reading, which can confuse the untrained tester and lead to erroneous decisions and controls.
There are two distinct equipment types commonly used to test and monitor atmospheres:
- Electronic portable gas detectors
- Colorimetric tubes
Electronic portable gas detectors are handheld units that are often programmable, and they provide instantaneous measurements to the operator of the equipment. They have the capability to detect and measure numerous gases and vapours depending on the sensors that are installed in the unit.
Electronic units are direct reading and display the content of gasses being measured constantly on screen. They also incorporate alarms to immediately warn users to atmospheric changes that present a danger.
Colorimetric tubes are used to detect a single toxic gas. Ambient air sample is drawn into a gas tube that houses a specific absorbing material that changes colour if the gas it measures is present.
Direct readings are made with calibration markings right on the tube, so measurements can be made as simply and precisely as reading a thermometer. A sample tube is inserted into the hand-held pump, and the pump is squeezed. A precisely measured volume of ambient air is drawn inside the tube where it contacts the reagent. Instantly, the reagent changes colour, reacting quantitatively to provide a length-of-stain indication. The farther the stain travels along the tube, the higher the concentration of gas. Note the scale mark on the tube where the stain stops and that’s the measurement.
There is a variety of equipment that is available to perform gas tests. A competent gas tester will know the limitations and operating procedures for each type. They must also understand the work area and the exact nature of the work to be performed as this will dictate the type of equipment needed and assist in determining where the testing is needed.
If performed properly, gas testing and atmospheric monitoring should help to ensure the safety of all personnel.
