Helping to deal with hazards effectively

Environmental sensors

By Morand Fachot

Sensors, devices that react to heat, light, radiation, chemicals or other stimuli, are central to our everyday life. They detect movement, the presence of humans, objects or certain substances and they switch on or off appliances, devices or machines to save energy or for other reasons. They can send visible or audible signals or be totally unobtrusive. They also play a central role in environmental and safety issues, in particular as regards hidden or invisible hazards, such as the presence of gases or chemicals. The IEC is pivotal in ensuring that the performance and quality of sensors improve constantly, allowing them to fulfil more tasks more efficiently as well as to save more lives.

Checking for possible radiation using a portable detector (Photo: NATO) Checking for possible radiation using a portable detector (Photo: NATO)


A significant number of fatalities that are not transport- or work-related happen at home and are caused by fires. Many occur at night when occupants are asleep, with most deaths resulting from smoke inhalation and poisoning rather than from burns. In case of fire, a timely warning allows residents to evacuate buildings unharmed. In countries where the compulsory installation of fire alarms in dwellings has been imposed, the number of fire-related deaths in domestic environments has been cut drastically. To give just one example, in the United Kingdom the number of deaths caused by fires in dwellings was more than halved between 1998, when only 9% of homes had fire alarms, and 2008, by which time some 90% of homes had been equipped.

Smoke detectors are the main fire alarm system. They can use different types of sensors and can be optical only, heat only, ionization only, or combine some or all of these types of sensors to provide better and quicker reaction.

All have different properties: optical smoke alarms are particularly good at detecting slow smouldering fires, ionization smoke alarms react quickly to fast flaming fires, detecting the alteration in ionized properties of air through smoke. Heat alarms are best for smoky and dusty environments: reacting to heat instead of smoke they are less likely to give false alarms .

Silent killer

Another major killer in the domestic environment is CO (carbon monoxide). CO is a colourless, odourless gas that results from the incomplete combustion of fossil fuels. It replaces oxygen in human blood, leading to dizziness, loss of consciousness, coma and eventually death. Although CO poisoning isn't usually provoked by fires at home, any fuel-burning appliance can be a potential source of fatal or hazardous CO levels. CO can be formed by open flames, space heaters, water heaters or blocked chimneys. This explains the relatively high rate of fatalities it causes in many countries during cold spells.

Fire alarms cannot serve as CO detectors. CO requires special detectors; however, dual CO and smoke detectors are also available. The installation of CO detectors is now required by law in some countries or states, such as California.

Gases represent a major source of risks. IEC SC (Subcommittee) 65B: Measurement and control devices, has prepared the IEC 61207 series of International Standards for gas analysers, which are used to identify certain constituents in gaseous mixtures. These standards concern high-temperature electrochemical sensors, paramagnetic oxygen, photometric and tunable laser gas analysers.

The most common and toxic gases and substances that need to be detected for health and safety issues are CO, hydrogen sulphide, ozone, chlorine, methane / natural gas / propane, CO2 (carbon dioxide), hydrogen, nitrogen, oxygen and hydrocarbons. Some devices can detect several of these gases at the same time.

Industrial environment

Workers in entire industrial sectors, like mining, oil refineries, paint shops or chemical plants, may be exposed to very different environmental conditions and to the presence of a wide variety of gases, some harmless, others toxic and some even presenting risks of explosion. Risks may be compounded by environmental factors such as humidity or temperature.

The wide range of hazards and the need to react in a timely fashion, mean that the use of dedicated detectors or sensors to identify the presence of harmful substances is absolutely essential.

Emergency and security services

The same applies in other sectors in which there may be exposure to hazardous substances. In case of industrial accidents, in particular in chemical plants, rescue workers, police or medical staff who intervene need to know the nature and seriousness of the risks they face. This is valid not just for major accidents but also for smaller ones. For this task, detectors are absolutely essential. Emergency services are using a very wide range of these devices, including multigas devices, to identify the nature of the danger.

Wide range of hazards

Not just chemical hazards but environmental factors too must be taken into account to minimize risks. Humidity control is an important factor in safety. IEC SC 47E: Discrete semiconductor devices, prepares IEC International Standards for humidity sensors.

Other IEC TCs also prepare International Standards for components used in detectors. For instance TC 20: Electric cables, works on cables for fire alarm systems, and TC 79: Alarm and electronic security systems, prepares IEC International Standards on EMC (Electromagnetic compatibility) immunity requirements for components of fire and security alarm systems.

Multiple applications, purpose-designed detectors

Sensors and detectors compliant with IEC International Standards are used by many safety equipment manufacturers. They are found in all domains, from farming or mining (detection of methane) to the medical environment (identifying content or pressure of oxygen and other gases such as nitrogen) and all industries that use gases or chemical products.

Advances in sensors have made a significant contribution to better safety in industry, with the production of tailor-made equipment and the availability of a wide range of devices, including portable and fixed detectors, single or multigas systems, radiation and compound specific detectors.

Most of these devices rely on IEC International Standards and comply with IEC Conformity Assessment systems to ensure their safe and reliable operation.

Checking for possible radiation using a portable detector (Photo: NATO) Checking for possible radiation using a portable detector (Photo: NATO)
IECEx-compliant wireless portable multi-gas monitor (Photo: RAE Systems, UK) IECEx-compliant wireless portable multi-gas monitor (Photo: RAE Systems, UK)
An open fireplace may spark a house fire and a blocked chimney can be a source of deadly CO An open fireplace may spark a house fire and a blocked chimney can be a source of deadly CO