Combustible Gas Detector

Combustible gas detectors are instruments that measure presence of flammable gases. Leaks of such gases are hazardous, as they can lead to fire or poisoning of humans or animals. HVAC service technicians use combustible gas sniffers in many situations, yet most frequently during the winter, when heaters and furnaces work to maintain comfortable leaving conditions.

What is combustible gas detector?

This question has two answers: a short and silly one and a longer, more helpful one. The first, of course, is that a combustible gas detector is a device for detecting combustible gases. What a surprise! But joking aside, let's dig a little deeper and get more technical and specific about what these devices are.

We'll cover the gases themselves in more detail below, but a simple explanation of combustible gas is a gas that will burn when mixed with air (oxygen specifically) and then ignited in some way. In other words, these gases, if loose in the air, will catch fire or explode.

Obviously, you'll want to make sure that you don't have gases floating around a building or a worksite that could potentially blow up and catch fire. To that point, these tools are often referred to as combustible gas leak detectors. This gives us a clue that these gases are often leaking from equipment, furnaces, storage containers, etc. These leaks are notoriously difficult to pinpoint and are next to impossible to find without the aid of a specialty tester. Enter combustible gas detectors.

These typically come in two forms. The first is stationary mounted units. We won't go into much detail on those since they are reserved more for those technicians and plant managers involved in manufacturing and related fields in which you need constant, stable monitoring at a defined location. The second form of gas leak detector, the type we'll discuss on the is page, are handheld combustible gas detectors.

Handheld gas detectors are most often designed with an elongated section with a grip of some kind and a readout. This readout varies from a digital LCD display, to an analog needle, to an LED bar graph style display. All of these different types of displays serve to help you determine the relative level of gas in an area. We'll get more into the specific operation of flammable gas detectors in another section below.

Almost all of these handheld devices are designed with a semi-rigid gooseneck style probe. This is especially useful for contractors and homeowners and the like, as this design makes it easy to place the probe anywhere you need to go (in contrast to the fixed mounted types we briefly mentioned). There are a few more features to look for in a gas detector, and we'll touch on some right now.

Some type of alert or alarm function is very useful. Many of the best detectors are designed with this feature, which alerts you to the presence of gas that crosses a certain threshold that would be considered dangerous. The most common types of alarm are audible (a beeping sound) and visual in the form of a particular LED flash. Some detectors also feature a vibration alarm, which can be especially useful if you're working in a noisy environment like a factory or construction site.

There are some features that distinguish the higher end detectors from more economical models (and we'll cover them in detail below). We'll hit just a couple right now. One useful feature is a fast warm-up. A one-minute warm-up time is a good benchmark to look for when selecting a meter. You'll also want to make sure the detector auto-calibrates to fresh air on startup. That will ensure you're detecting accurately when you work.

One more useful feature to look out for is adjustable sensitivity. We'll cover the usefulness of this feature in more detail in the operation section of this article, but suffice it to say that adjustable sensitivity will make your job a lot easier.

Another thing to keep in mind is that the probe tip sensors do degrade over time, so you want to be sure to replace them every 2-3 years. Each manufacturer will have specific guidance on how to best maintain the detector that they produce.
 
Those are the basics of combustible gas detectors, in terms of what they are and briefly what to look for. Now let's address how they actually function.

How does combustible gas detector work?

This is a great question, and again there is a simple, obvious answer and a more complicated one. On the simple level, the detector has a sensor in the tip (we're dealing here just with the handheld variety) that finds combustible gases and alerts you to their presence. As for the complex answer, let's do a mini deep dive into the science and technology behind these tools.

The detector uses one a few methods to compare a gas sample it takes in to a reference scale, and if the detected concentration exceeds the preset level, the detector will alert you in one of the ways we discussed above (visual or audible alarm, vibration, etc.).

There are two main types of combustible gas sensors. Most manufacturers don't indicate the type of sensor unless it is a much higher-end model, and they are practically equivalent, but it's good to note the difference as it will affect your buying decision and has some influence over the accuracy of the meter. Though for most day to day purposes, both types of sensors are quite good.

The most common type of sensor is a so-called "passive" sensor or electrocatalytic sensor. This type of sensor has been around for a few decades and works on a relatively dependable and straightforward principle. This principle is that a combustible gas can be oxidized in order to produce heat. The sensor is thus designed to read this change in temperature and convert it using a particular circuit a Wheatstone Bridge into a reading that will alert you to a dangerous amount of gas in the air. In other, less technical words, the sensor passively reads the temperature change that the gas creates.

The other type of sensor is an "active" sensor or infrared sensor. This type of sensor emits an infrared light, hence the term "active, since the sensor is actually producing a type of signal. The meter also has a light detector inside it. So, the sensor will emit an infrared light that passes through the gas sample. Then the light detector will pick up various degrees of distortion to the original infrared signal and convert this difference into a value based on the gas density. In other words, the more gas, the more the distortion of the infrared signal. By this method, the combustible gas detector will "know" is there is a dangerous level of combustible gas in the air. It's worth noting too that this kind of infrared technology is very accurate and can actually be used in higher-end detectors to not only alert you to the presence of combustible gas but even determine the concentration in the air.

No, it is not, so you need to use a different class of instrument to detect it.