Gas and Flame Gas Detection for Complete Safety
Lower explosive limits (LELs) are the lowest concentration of a gas or vapor in ambient air that can ignite an explosion. Because of the amount of risk associated with flammable and explosive gases and the problematic confined space entry regulations, detectors that keep LELs in mind are seen as the go-to technology for flammable gases.
LEL flammable gas detectors are clearly an important part of a gas detection program, but due to their underlying technology, they are more effective for measuring relatively high flammable gas concentrations. Typical fire regulations call for gas alarms at 10-20% LEL. However, this technology is often not very reliable at 5% LEL and below, despite often being deployed as the sole detection technology for flammable gases. Although LEL flammable gas detectors are often used in industry, they are not very effective for measuring gases.
Although less frequently used, high-quality flammable gas sensors optimized for the ppm concentration of a gas have been developed and are available for companies to utilize. These sensors are ideal for gas detection scenarios where the concentrations that must be measured are significantly below the normal LEL range of a typical flammable gas detector.
A common situation in semiconductor and gas plants, among other industrial settings, is the use of dopant gas bottles with a small amount of one substance in a high concentration of flammable gas; typically, over 90 percent flammable gas. With PH3 (dopant) gas concentrations of 10 percent, the bottle contains 90 percent hydrogen. That is well above 100% LEL for hydrogen (4% by volume). If you had a catastrophic failure of the system and the gas was freely flowing into ambient areas or exhaust, you could have explosive mixtures that a normal high-concentration LEL sensor would pick it up.
However, gas releases in gas-detected areas are rarely catastrophic. Usually, they are very small leaks that develop over time. It’s important to know that a typical standard 100% LEL sensor will not detect this small leak event at all, and that big leaks almost always start as small leaks. From the perspective of increasing safety and hopefully preventing a catastrophic leak, there are clearly some advantages of implementing more in your gas detection system rather than just a flame detector.
There are many other scenarios where measuring flammable gas concentrations at low levels will result in a higher level of safety. It’s widely encouraged that it’s always best to have as early an indication of a potentially flammable/explosive gas mixture leaks as possible and that ppm gas detection technology should be utilized as part of the gas safety system.
Safety is our top priority, which is why Otis Instruments offers a variety of Wired and WireFree easy-to-use, robust and configurable gas detectors. We also offer flammable gas detection instruments, as well as telemetry and automation & controls services through Otis Link for remote monitoring and system integration. Made in the USA, our high-quality products are capable of detecting both toxic and non-toxic gases for diverse applications. If you would like more information about implementing both gas and flame detectors on your site for complete safety or would like assistance regarding gas detection for your application, contact our team today.