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Electronic Gas Monitors

Many industrial worksites produce atmospheric hazards that could put their employees and the environment at risk. Toxic environments such as carbon monoxide, hydrogen sulphide, and corrosive atmospheres like ammonia, chlorine and sulphur dioxide are common atmospheres that need monitoring to ensure that the legal limits are not exceeded. Other dangerous atmospheres in the petroleum, construction and manufacturing industries include oxygen deficiency and flammable or explosive environments.


In the Alberta Labour Code, employers are required to implement a WHMIS program to train employees about chemical hazards. Workplace Hazardous Materials Information System provides the exposure limits that employees must not exceed without engineering , administrative controls or personal protective gear.


Electronic gas monitors are a popular option to determine if the atmosphere workers are entering might be immediately dangerous to life and health. They can be set to provide audible and visual alarms at preset exposure limits to alert employees to changes in air quality.


There are a multitude of choices when considering gas detection equipment.

Personal monitors are a less expensive option but are limited to one gas. They are met to be worn on a persons body, exposed to the atmosphere. They can provide continuous monitoring but may be limited to ranges below 500 ppm. Unfortunately, if the alarm rings, the monitor is picking up a rise in gas at close range to the workers nose. They may be inhaling the toxic chemical while the alarm is ringing.


Portable continuous monitors have sensors for a variety of gases, such as oxygen deficiency and enrichment, H2S and CO and the lower explosive limits for hydrocarbons. They can be set to issue a warning at a low and high alarm level and often have a wider range of detection capability. These portable placed monitors can be used for a team of personnel or set up between a worker and the potential source of the gas release. They are more expensive than personal portable monitors and must be positioned correctly to be effective warning systems.


Fixed continuous monitors issue a site wide warning and provide automatic response capabilities. Sensors can be placed at the most predictable sources for gas releases and may be tied in to a control room or central display area. The area that is exposed can be shut down, ventilated and alerted to rescue crews. Instrumentation trained personnel can monitor the area and evacuate personnel from the gas environments. They are significantly more expensive and require personnel on shift continuously.


Although electronic devices can be life savers, they have distinct problems. Sensors tend to be ruined by corrosive or wet environments, or over ranging them with high levels of gas. Dust can clog sensors and silicone will ruin the sensor heads. In cold environments, the batteries tend to die.


They require significant care, such as bump testing , and calibration. Maintenance problems could include replacing the lcd displays and batteries. It is wise to consider

whether a calibration service is easily accessible with quick turnaround if repairs are needed. The cost of calibration can quickly exceed the original cost of purchasing the detector.


When considering whether to purchase an electronic monitor, compare the costs and maintenance requirements to keep them accurate versus the convenience of renting equipment on a per needs basis.


Arliss T E Levine, CRSP, CHSC

Certified Health and Safety Auditor