When it comes to handling gas-related risks effectively, the key is being able to detect them early on so that you can take appropriate action to protect staff, the workplace and equipment.
There are many detection means available, ranging from very simple devices to complex, high-performing equipment. You may need to choose a very specific type of detector or just the opposite – have a device that is capable of detecting a wide variety of gases depending on the application.
Portable Gas Detectors
Designed to be clipped onto work clothes to protect the operator. These are personal protective devices but they are not classified as category 3 Personal Protective Equipment (PPE). They are used primarily to:
- Check compliance with Occupational Exposure Limits (OELs) at workstations with regard to the respiratory tract, for a representative length of time, such as: 15 minutes (Short-Term Exposure Limit, or STEL) or 8 hours (Time-Weighted Average, or 8-hour OEL)
- Check for leaks in pipes by detecting traces of gas.
- Check the hygienic conditions of the environment before entering a high-risk zone (confined spaces).
- Monitor the air quality when carrying out work in places that are difficult to ventilate.
Fixed Gas Detectors
Comprising one or more detector heads, they are installed in buildings or on equipment to protect both staff and the facilities.
They are usually made up of a sensor (sensitive element or detector) and a transmitter (which may consist of a display, an alarm relay and a signal output analog of 4-20mA). The sensor converts the gas concentration into an electrical signal and the transmitter processes the electrical signal emitted by the sensor. These detectors are often connected to sub-systems such as a sounder and beacon to warn staff to evacuate the area.
Area Gas Monitors
Transportable detectors that can be hooked up to create a gas detection system (with wires or wireless) that covers and marks out a given work area for a temporary period of time. They are often used on building sites.
- Used as part of an expandable network, the monitor sends alerts from one component to another via a cable or wireless radio communication.
- Connected to a wireless centralisation system, the gas concentration measurements can also be reported in order to guarantee precise monitoring of the area.
Colorimetric Gas Detectors
These detectors use chemical reagents absorbed on an inert support material. The reagents are specific to the gas to be detected and change colour when exposed to that gas.
There are various techniques, but the best known is the colorimetric tube that indicates the presence of a gas rather than its concentration. These are the simplest detectors for measuring a vast range of substances (around 200 explosive or toxic gases and vapours). Made up of a glass tube to be broken at both ends, they are filled with specially-impregnated granules that can determine various types of pollutant substances. The pump draws a sample of the surrounding air into the tube. If the pollutant in question is present, the indicating layer changes colour. A specific scale is printed onto each tube, so that the concentration of gas (or vapour) in the atmosphere can be measured by observing the length of the coloured part. They have a long shelf-life, which makes them perfect for your occasional measuring needs.
Another solution is the optical analysis system, which gives a more reliable measurement. These sophisticated versions combine the colour change on a chemically-impregnated strip of special paper and an optical analysis system. They give quick, targeted measurements of concentration levels expressed as ppb (parts per billion).