When gas contacts, a gas sensor the sensor measures its concentration and sends a signal to a readable display. The signal can be one of many types, including pulse and either voltage or current analog.

Some gas sensors have complex readouts, while others, like simple gas level sensors, continuously read liquid fuel levels in a vessel or signal an alarm at predetermined levels or concentrations. Various gas sensors read out more than one type of measurement:

1. Lower explosive limit (LEL) or lower flammable limit (LEL), usually for gas detection sensors.

2. Percent volume (usually for liquids).

3. Trace presences of gas in parts per million (ppm).

4. Leakage in volume; for example, ml/min.

5. Respiration or consumption, usually measured in volume units per hour.

6. Density; for example, mg per meters cubed.

7. Spectral signature of heterogeneous or nearly homogeneous gas.

Action Steps
The best contacts and resources to help you get it done

Locate a gas sensor manufacturer that carries sensors tthat detect applicable gases

There is the multi-gas sensor that serves many generalized purposes, but other sensors detect specific target gases. Common gases include carbon monoxide, fluorine, mercury vapor, nitrogen dioxide, oxygen, sulfur dioxide, humidity or steam, refrigerants, hydrocarbons and many others. However, if you need to detect and quantify rarer gases, you may have to do a more extensive search to find the right sensor.

I recommend: Figaro USA lists their semiconductor gas sensor products by target gas. Along with their detailed pdf documents on each product, you'll find their organization very useful. Control Instruments Corporation has a convenient and extensive table of gases on their website that will help you find what you're looking for in their products section.

Buy gas sensors specialized for your application

When buying a gas sensor, take operating humidity and temperature into account. There are also many special kinds of gas sensors, like calibration gas sensors, the optical gas sensor and those mentioned below.

I recommend: Acme Engineering carries many gas sensors, including wireless gas sensors, a single-point diesel fumes detector and many others. A source specifically for industrial applications is Sierra Monitor Corporation. Their products include controllers and modular sensors. Additionally, kTSensor includes the infrared gas sensor among their infrared technologies.

Avoid toxic gas catastrophes in your home or business with gas detection systems

Carbon monoxide (CO) is a famous toxic gas. But there are many other toxic and combustible gases, like Cl2, H2S, NH3, PH3, and SO2. Single sensors can cover the bulk of them.

I recommend: RKI Instruments carries toxic gas detectors in multiple forms, including wall-mount, portable and even one that resembles a wrist watch. Net Safety Monitoring, Inc. is another source. They have a special model that requires very low power: only 32 mA.

Tips & Tactics

Helpful advice for making the most of this Guide

• •  If it's published, the response time of a sensor is good to know. Also, check the maximum distance the sensor can be from the source and still detect. The minimum amount of gas that must flow over the sensor for detection is another important consideration.