Gas detection tubes
Simple snapshot devices using colorimetric chemistry to make a measurement. Simple to use, with a wide range of specific gases available, but are relatively inaccurate and offer just a momentary reading not continuous monitoring.
Disposable personal monitors
Low cost, minimal maintenance devices providing personal protection against gases such as hydrogen sulphide, carbon monoxide and ammonia. Simple, and affordable personal safety, but are relatively inaccurate, have a limited lifespan and are not particularly environmentally friendly.
Single channel personal monitors
Personal protection devices offering a wider variety of gas sensors than disposables. Easy to use and slightly more accurate, they have an unlimited lifetime, but require regular calibration and maintenance.
“Four gas” monitors
Simple multiple gas detectors, sometimes disposable, configured with (usually) methane LEL, oxygen, carbon monoxide and hydrogen sulphide sensors. These are the most common confined space monitors and are simple and efficient. They need regular calibration and maintenance, but can be very cost effective. Warning: although these gases are commonly found in confined spaces it is not a given and often these devices can be used as a standard when no real risk assessment has been done. Another gas cold be present or in place of these.
Multi gas monitors
Personal, portable gas detectors with the capability to house four, five or up to eight gas sensors. Often with integral electric pumps, these are more versatile and adaptable devices, but they require greater level of knowledge to specify, will require regular calibration and maintenance and will be more expensive to purchase and operate.
Transportable devices, usually with a similar specification to the multi gas monitors. The offer a louder sounder and greater visibility of the alarm and can be linked together to provide a wider area coverage, they will be heavier and require regular recharging to remain in use. They still only detect gas in the immediate vicinity of the detector.
PID (Photo Ionisation detectors)
A simple device for providing continuous measurement of VOCs (volatile organic carbons) at low (ppm or ppb) levels for occupational exposure measurements. Reliable and accurate, but not specific to any VOC, and not responsive to all VOCs. Requires regular maintenance and calibration and less tolerant of damp and dirty environments.
A self-contained fixed gas detection system, with maybe up to eight or ten fixed point detectors. The system will usually include some simple alarm triggers, such as relays to activate alerts and possibly provide simple mitigations steps such as shutting valves or opening vents. Cost effective and simple, but not necessarily easy to integrate into wider safety systems, or to produce more sophisticated outcomes.
Complex ESD systems
Often with many channels of detection of multiple gas types (combustible, toxic, open path, etc) and with sophisticated alarm logic and functions. These are typically for larger more complex installations. They will often incorporate fire detection and suppression systems and interface with broader safety systems. These will be expensive and complicated to create often meeting wider safety standards such as SIL (Safety Integrity Level).
Detection system which uses a beam of infra-red light to detect gas over an extended area. It is a cost effective and reliable way of detecting gas over relatively large distances, but does not provide any indication of the gas location and aggregates the reading over the full length of the detection path. Virtually limited to hydrocarbons, and subject to blockage it is not suitable for every application.
Available as technology for both portable and fixed gas detection, wireless is a relatively new addition to gas detection as it was previously thought too prone to interference and blockage to be reliable for gas safety. Within those limitations it offers excellent savings on installation for fixed gas and an easy way to connect portable and transportable devices together.