Gas Detection

Hazardous Area Gas Detection

Crowcon Hazardous Area Gas Detectors (ATEX Certified) Zone 1 & Zone 2. Contact T&D for with your enquiry.


T&D distribute Gas Detectors, Gas Monitors & Equipment (Portable & Fixed) for the monitoring of toxic and flammable gases in industrial and hazardous areas – this includes Crowcon.

T&D sales engineers can specify safe gas detection equipment for any industrial application;  including ATEX & IECEx certified gas detectors for use in Zone 1 and Zone 2 hazardous areas in the oil, gas and petrochem industries.

Gas Detectors - Zone 1 Zone 2 ATEX Certified

Gas Detectors for Industrial & Hazardous Areas: fixed and portable gas detection for Ammonia, Carbon Dioxide, Carbon Monoxide, Chlorine, Chlorine Dioxide, Hydrogen Sulphide, Methane and Nitrogen Dioxide.

➡ Read Blog: Gas Detection In The Food Processing Industry Using Portable Gas Detectors

Gas Detection Detector - Food Industry

Reliable gas detectors are an everyday safety requirement in the food processing industry – detecting potentially flammable and toxic gases such as carbon dioxide, natural gas and oxygen.


How To Select & Specify

For those working in a confined space where toxic or flammable gas could be present, the use of the correct gas detector can mean the stark difference between life and death.

Information gathered in the late 1970’s and early 1980’s found that 65% of all those who died in confined spaces were unaware the space they were entering was a gas hazard. Furthermore, over 50% of deaths that occured were the rescuers and over a third of the deaths occured after the confined space was deemed safe and the gas detector had been removed.

Prior to entering a confined working space where gas may be present there are 3 hazards that are tested for; combustibles, oxygen deficiency and toxics. Depending on the gas sensor configuration, the correct detector should easily identify the hazard posed to workers.

When selecting the most suitable gas detector for flammable or toxic gases several criterion should be considered :

  • Is a fixed or portable gas detector required?
  • Is there a single defined gas hazard, or do you need a multi-gas detector to monitor several gases?
  • Which gas(es) require detection?
  • Does it require ATEX/UL or other hazardous area certification or approvals?
  • Is the area to be monitored for gas leaks hot or wet?
  • If a fixed gas detection system:
      • a) Is the sample to be monitored of high pressure or flow?
      • b) Does it need a controller or will the gas detectors communicate with an existing system?
      • c) If it is an existing gas detection system, what type of controller is being used

gas detectors – PORTABLE OR FIXED GAS DETECTION?Gas-Detectors

The range of gas detectors available from Thorne & Derrick are either fixed or portable with both types having different benefits and features. The selection of the correct gas detection equipment is vital in order to provide an adequate level of protection and comply with safety regulations.

By deploying portable or fixed gas detectors, companies can ensure the safety of their workforce, prevent unnecessary damage to their equipment and reduce any downtime.

Put simply, fixed gas detectors protect plant; portable gas monitors protect people.

Portable Gas Detectors – these monitors are usually clipped or attached to clothing/overalls providing close detection of gases (single and multi-gas) and can be moved between zones. Portable gas detectors are extremely portable and can be calibrated to detect a range of flammable, toxic and hazardous gases.

Fixed Gas Detectors – fixed or stationary gas detectors are designed to be permanently attached to a working area and will typically be hard wired into mains electricity to provide 24 hour protection and detection of gases.


Portable gas detectors are typically smaller, handheld devices that provide gas detection in smaller locations and are often used in confined spaces or working areas – mobile, transferable and transportable.

Portable gas detectors are compact, handheld monitors used for testing an atmosphere in a confined space before entry, for tracing gas leaks or to give an early warning of the presence of flammable gas or vapour when hot work is being carried out in a hazardous area.

There are many commonly occurring gases that can cause a threat to life and infrastructure including carbon dioxide, methane, sulphur dioxide, hydrogen sulphide, copper sulphate and carbon monoxide. These gases have varying effects on the human body where some are undetectable by humans as they are odourless and colourless, others can have devastating effects within seconds and must therefore be detected immediately.

What’s A Confined Space?

The UK HSE defines a confined space as ‘any place, including any chamber, tank, vat, silo, pit, trench, pipe, sewer, flue, well or other similar space in which, by virtue of its enclosed nature, there arises a reasonably foreseeable risk.’

Crowcon Gas-Pro is a confined space entry monitoring solution for workers and fleet managers.

Gas Detectors - Confined Space Gas Detection

Gas Detectors: Crowcon Gas-Pro protects confined space workers detecting 5 gases including potentially explosive gas in low oxygen atmospheres.

Fixed Gas Detectors

Fixed gas detectors are permanent, stationary installations and provide continuous monitoring of a location, plant and equipment. They give early indication of the presence of hazardous, flammable or toxic gases/vapours and are fixed (“hard wired”) into a mains electricity supply to provide constant, round-the-clock protection.

A fixed gas detector is permanently installed in a selected location to provide continuous monitoring for gas leaks on plant and equipment. The gas detector provides early warning of flammable or toxic gas leaks, or for monitoring concentrations of gases and vapours within the plant including potentially explosive atmospheres, such as Zone 1 and Zone 2 hazardous areas.

Fixed gas detectors are commonly specified for monitoring gas leaks in confined spaces where flammable gases accumulate – this includes SF6 gas detection for high voltage GIS (Gas Insulated Switchgear) applications.

T&D Gas Detection Gases


Gas Detection in Zone 1 & Zone 2 Hazardous Areas

Hazardous working areas exist within many industries and the classification is used to identify areas where special precautions must be taken over sources of ignition in order to prevent fires and explosions.

Once a working area has been identified as hazardous it must be classified into a zone based upon the frequency and persistency of the potentially explosive atmosphere. This then helps to determine the controls needed on potential sources of ignition that may be present in the area.

  • Zone 1 hazardous areas are classified as a working area where the presence of explosive gas is likely to occur during normal working conditions
  • Zone 2 hazardous areas are classified as working areas in which explosive gas is not likely to occur during normal operation and if it does it would not be for an extended period of time.

The selection of equipment is vital when working within hazardous areas. Gas detection equipment must be intrinsically safe and not be a spark hazard or source of ignition.

Gas Detection

Plant Safety & Integrity – 3787 people died in the Bhopal Disaster from the effects of a serious toxic gas escape from a chemical factory.

Oil & Gas Industry Report

Better gas detection technology could be behind an increase in the number of oil and gas leaks reported on the UK continental shelf (UKCS) in 2015, according to the Oil & Gas UK 2016 Health & Safety Report – the report confirmed the number of offshore hydrocarbon releases went up by 9% to 87 in 2015. Download and read report here.

Gas DetectorsHazardous Area Gas Detection

Reliable gas detection in potentially explosive atmospheres can avert catastrophe, danger and risk – providing an advanced lifesaving warning to people and protecting plant against fire and explosion. The detection of dangerous flammable and toxic gases is a first critical step to securing worker safety in hazardous area industries – the manufacturing, processing, storage and transportation of toxic and flammable chemicals poses significant risk hazards. Robust and correctly specified gas detectors provide an essential role in incident or accident mitigation with the ability to detect multi-gases and measure the gas concentration in the atmosphere. Life threatening gas leaks can be invisible to the naked eye, odourless and impossible to sniff-out. Modern gas detection systems for both industrial and explosion-protected hazardous areas could be the stark difference between life, serious injury and even death.

Avoiding ignition risks from gas detection systems

Dangerous Substances and Explosive Atmospheres Regulations (DSEAR) places certain restrictions on the type of equipment that can be used in hazardous areas and areas where explosive atmospheres may occur.

Any workplace where an explosive atmosphere could occur should always be:

  • Classified into hazardous zones – zone 1 or zone 2
  • Protected from any sources of ignition by using equipment certified as suitable for use within hazardous areas that have the ‘CE’ and Ex’ markings. These markings show the conformity with the Equipment and Protective Systems Intended for Use in Potentially Explosive Atmospheres Regulations (1996).

Gas Detector Inspection, Maintenance And Calibration

Fixed gas detectors should be maintained, inspected and calibrated during the plant maintenance schedule as the performance of many fixed point gas detectors deteriorates over time and the rate of deterioration depends upon the sensor and operating conditions.

Certain operating conditions can be more corrosive due to dust or high corrosion levels and these factors will affect the calibration and maintenance.

For portable gas detectors the user should consider the type of sensor, operating conditions, required use and accuracy of the detector. Portable gas detection equipment should only be used if in good condition and functioning correctly. They should also be tested prior to each use in order to guarantee accuracy and functionality.

Crowcon – Gas Detection SPECIALISTS

 See more Crowcon.

Crowcon F-Gas : Gas DetectorS For Freon Gases  

Fluorinated (Freon) gases, which include hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), hydro-chlorofluorocarbons (HCFCs) and sulphur hexafluoride (SF6) are a family of man-made chemicals containing fluorine. These ’F-gases’ are extremely powerful greenhouse gases that trap heat in the atmosphere, contributing to global warming – most are between 1,000 and 20,000 times more powerful than CO2 gas in terms of their impact on the atmosphere. Not only are F-gases harmful to the environment, they are also extremely toxic and represent a significant health risk if inhaled.

SF6 gas also poses an asphyxiation risk, as, once inhaled, it may be too heavy to expel from the lungs.

 the 5 most important freon f gases
  • Freon 11 Trichlorofluoromethane Gas
  • Freon 12 Dichlorodifluoromethane Gas
  • Freon 22 Chlorodifluoromethane Gas
  • Freon 113 Trichlorotrifluoroethane Gas
  • Freon 114 Dichlorotetrafluoroethane Gas

Guidance document relating to the impact of F Gas and Ozone Regulations on stationary refrigeration, air-conditioning and heat pump equipment (RAC systems).

Crowcon F-Gas : Fixed Gas Detector For Freon Gases from Thorne & Derrick on Vimeo.

For complete information, specification and technical details on Crowcon Gas Detectors please refer to the sections listed below.