FM Approved Point Gas Detection
Gas detection technology is widely used in industry to protect facilities, processes and personnel from unexpected leaks and discharges of combustible or potentially harmful or toxic gases and vapors. Gas detectors can trigger alarms, record events, provide time for intervention or evacuation, activate ventilation, or even release water mist or CO2 to suppress ignition if a gas cloud is forming.
Fixed point and open path (line of sight) gas detection systems are typically used by oil, gas, power generation, chemical process and waste facilities to create layered protection. Gas detection technologies include catalytic or electrocatalytic, electrochemical cell, solid state sensors, ultraviolet or infrared (IR) detectors.
Fixed point detectors are typically used to protect selected, high risk areas and may be deployed in multiples or in a grid pattern. This type of detector may also be deployed in handheld variations for spot checking or use by crews entering high risk zones.
Open path or line of sight detectors—IR, laser, ultraviolet —are most often used to monitor open spaces above rows of valves, tanks or pipelines.
When monitoring for combustible gases, detector measurements are referenced to the target gas’s lower flammable limit, or LFL. This is the minimum concentration of gas needed to burn in ambient air. This number is expressed in a percent by volume. For example, when the ambient air is at least 5% methane, a spark could cause an ignition. The LFL varies depending on the gas. For instance, propane has an LFL of 2.1% while ammonia is 15%.
Gas detectors used to monitor toxic gases or vapors must measure gas concentrations at very low levels, usually parts per million (ppm). There are many different units of measure and ranges because exposure levels (threshold limit values) vary depending on the gas. In addition, many gases are both toxic and combustible. Ammonia, for instance, has a toxic level that is far below its LFL and therefore a combustible gas detector can never be used as a toxic gas detector.
Testing Required for FM Approval
The National Electrical Code (NEC) requires that a gas detector be evaluated by an organization acceptable to the authority having jurisdiction (AHJ). This can be either a manufacturer or a certified third party, such as an Occupational Safety and Health Administration (OSHA) accredited Nationally Recognized Testing Laboratory (NRTL) such as FM Approvals.
While OSHA accredits NRTLs, it does not require the NRTL to certify specific products to a specific list of standards—that is left up to the NRTL.
Since it is left to the NRTL to decide what testing is necessary, not all NRTLs perform performance testing or allow performance testing to be optional. Combustible gas and even toxic gas detectors are often tested for electrical safety, but not always for performance.
Unlike all other testing and certification organizations, an FM Approved gas detection system has not only been evaluated for electrical safety and for use in a hazardous location, but is also tested for performance based on the manufacturer’s specifications. It will detect the gas that it was designed for. Standard 6310, Approval Standard for Combustible Gas Detectors, and Approval Standard 6325, Performance Requirements for Combustible Open Path Gas Detectors, require combustible gas detectors to meet a range of physical durability, electrical and performance tests. In addition, manufacturers must demonstrate an acceptable quality control program and submit to regular surveillance audits of locations manufacturing FM Approved products.
Benefits and Availability
FM Approvals is the only certification organization in the world that mandates performance for ALL types of gas detection (i.e. combustible, toxics and oxygen depletion) as a requirement to earn its certification mark. Other certification bodies throughout the world have a variety of options between electrical safety and performance testing. The FM Approvals certification mark always means an FM Approved gas detector has been evaluated for performance as well as electrical safety.
When it comes to gas detection systems, the stakes are high and the dangers are real. It’s a fact that performance evaluations for gas detection systems are not mandated by local jurisdictions or OSHA. Since gas detection systems do not have any mandatory performance testing requirements, there are products available on the market for which performance requirements have not been verified or certified by an NRTL or other third-party certifier.
Do you really want to stake the integrity of your operation and safety of company employees on a gas detection system that has not been performance tested? FM Approved gas detectors and detection systems should be recommended wherever possible. While it’s true that a non-FM Approved gas detection system may cost less than an FM Approved system, a single adverse incident can wipe out this small savings and have other devastating and lasting consequences.
But What About...
The best place to start any pricing comparison is the manufacturer’s website. The Approval Guide, an online resource of FM Approvals, provides links to the websites of most manufacturers that produce FM Approved products along with the listing for the products. That link will often go you to a pricing sheet, or at least to a representative who can explain the actual cost that a manufacturer is charging his customers.