Atmospheric monitoring is a key tactical priority during response to a gas or liquids hazardous materials incident. Determining where hazardous vapors are present in relation to areas of public occupancy, and potential ignition sources, is a critical step in responding to a spill or leak.

Many response organizations are equipped with atmospheric monitoring equipment such as multi-gas detectors, individual gas detectors, and in some cases, gas sampling equipment. Regardless of the type of detector used, there are some common guidelines to be followed when using these devices.

Conduct a thorough Scene Size-Up – Before conducting atmospheric monitoring operations, the Incident Commander should ensure that a thorough scene size-up is conducted to identify any hazards that may pose a threat to responders and to the public.

Identify the Product – Identifying the product involved in a hazardous materials incident is a key step in the response process. For pipelines, this identification can be made by locating a nearby pipeline marker. In some cases, pipelines transporting different products may be located in adjacent rights of way, so it’s very important to call the emergency number on the marker to notify the operator and determine the exact product involved.

Ensure That You Have the Right Equipment for the Task - When using monitoring equipment, it is important to remember that calibration of these devices is performed using specific calibration gas. For example, when monitoring for one type of flammable gas, such as propane, using a combustible gas indicator (CGI) calibrated to methane (natural gas), a conversion factor will have to be used to determine the accurate gas concentration. The bottom line…know your product and know your equipment!

Other Key Points to Remember - Here are some other things to keep in mind related to use of atmospheric monitoring equipment:

• Maintenance - When was the last time your monitoring device was calibrated? How about the last time the batteries were changed or charged if rechargeable?
• Know What it is Telling You - Ensure that your personnel are properly trained in how to use the equipment AND in what it is telling them. “Chief, I have fifty-percent!” Is that fifty percent of the Lower Explosive Limit (LEL) or fifty percent gas? The devil is in the details, and training in this area is critically important.
• Use Your Resources – Pipeline operator personnel have atmospheric monitoring equipment and are well trained on how to use it. Rely on them to help you determine the existence and location of hazardous vapors so that you can make informed strategic, and tactical response decisions.

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