Explosimeter – Gas warning device for explosive gas mixtures

What is an explosimeter?

An explosimeter is a portable or stationary instrument that measures the concentration of the combustible portion of the atmosphere. The measuring range is from 0 to 100 % LEL (lower explosion limit). Above LEL the gas mixture would be explosive. This is where the name Explosimeter comes from. Consequently, the alarm thresholds are set far enough below the end of the scale, so that if an alarm sounds, there will be enough time to take safety measures.

Explosimeters are used to check the safety of certain areas or are used during an incident. Another application would be entering potentially explosive areas (zone 1). For this application, portable devices with built-in pumps are commonly used. These instruments can take a sample before entering the area.

However, there are also workplaces where flammable gases may occur during the process. These are of course continuously monitored.

Alternatively, explosimeters are also called EX measuring instruments.

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How does an Explosimeter work?

The gas warning device indicates the content of explosive gases in the air. It shows what percentage of the lower explosion limit (LEL) has already been reached. Only when 100 percent is reached, a spark, a flame or a hot surface can ignite an explosion. In order to have enough time for protective measures, the alarm thresholds are set to much lower values, e.g. Alarm 1 at 20 % LEL, Alarm 2 at 50 % LEL. If the alarm thresholds are exceeded, the explosimeter gives a visual or audible alarm. Stationary devices activate peripheral alarm devices such as flashing lights or horns.

Setting the alarm thresholds well below the LEL ensures a sufficient safety buffer. There is sufficient time to move away or take other protective measures such as forced ventilation. To enable explosimeters to warn of the danger of potentially explosive gas mixtures in areas that are difficult to access, such as manholes, many portable models are equipped with a small pump, a hose and a float probe as accessories. This tube allows the instrument to draw a gas sample. The float probe prevents water from being sucked into the unit.

What is calibration gas?

An explosimeter is calibrated to check for specific gases. The physical properties of many combustible gases are different. It is therefore essential to select the appropriate calibration gas for the intended application of the instrument. Erroneous measurement results can occur if the calibration gas used is not tailored to the application. If fuels or solvents are to be measured, nonane is often used as a reference. Nonane has a very low LEL. Therefore the instrument is set to high sensitivity. Therefore  this setting is called a safety calibration. Typical vapors that must be frequently detected include toluene and acetone, which are used as solvents for paints and varnishes. A typical gas would be methane, the main component of natural gas.

Where can I find Explosimeter?

Compur Monitors is one of the leading suppliers of stationary and portable gas measuring instruments and gas detectors. Our experience spans more than four decades back to the 1970s. An overview of our models as well as detailed data sheets and operating instructions for download can be found on our website.

If you have any questions about our products, we will always happy to help you. Please use our contact form, send us an e-mail or give us a call. We look forward to advising you in detail on all questions concerning our gas detection instruments and explosimeters.