Generally speaking, gas detectors are mainly divided into two categories, namely stationary and portable. Both types utilize a variety of gas sensors to detect gas or vapor hazards. Both types have their own advantages and disadvantages. Therefore, it is extremely important to understand the nature of the gas or vapor hazard you are trying to mitigate in order to determine the most appropriate detection solution. Risk assessment is always the starting point. Mitigation will take several forms – gas detection is one of them. At this point, it is usually best to let the gas testing company find a suitable solution.
Fixed Gas Detectors
Permanently installed in the field, fixed gas detector for continuous monitoring of the environment. Fixed detectors work similarly to fire and smoke alarms. Detectors for the target gas are deployed on site and connected to the control panel. The controller monitors the detector and sets alarm conditions based on gas levels. Trigger an audible and visual alarm at a basic level to alert personnel. More advanced installations can alert other monitoring systems, activate and disable systems, log and trend data, connect to cloud-based systems, and more. This is one of the main benefits of a stationary gas detector over a portable one.
Fixed detectors will monitor a limited area/volume around the detector, typically a 5M radius. This means placement needs to be carefully considered for best performance. Detectors may be diffusion types or pump (aspirated). The right choice is application dependant.
Pros:
24/7 continuous detection of the environment
Can perform executive actions for example shut off gas supplies and provide site-wide alarms
Remote alarms possible including GSM text and email alerts and cloud monitoring
Clear unambiguous alarms if specified correctly
Events can be recorded for HSE requirements
Data can be logged for trending
Cons:
Accurate detection is limited to gas that diffuses into the sensing inlet – requiring strategic placement of detectors
Capital installation cost can be expensive depending on the amount of equipment required
Demand constant power supply
Requires regular service checks – just like a fire alarm system
Portable Gas Detectors
Portable gas detectors are designed to be carried or worn clipped to an item of clothing. They form part of a person’s PPE. This category of detector is a life safety device designed to provide alarms to the wearer when target gas levels exceed safety limits. They should not be mixed up with handheld gas leak detectors or analysers which are not intended as life safety devices. They can screen for hazardous species that may enter an operator’s breathing zone or be used for confined space entry testing. Portable gas detectors can be just for a single gas or may monitor for up to seven gas types. They may be diffusion-based or be pumped depending on the application. Portable gas detectors are intended for use where it is impractical to fit a fixed system.
Pros:
Easily deployed
Directly protects an individual
Can be integrated with man down or lone worker alarms by GSM
GSM linked units can be tracked centrally and monitored remotely
Cons:
No automatic responses
Operators must be trained
Requires daily bump test
Does not provide 24/7 monitoring
Only protects a single user
The user is wearing the unit and so is in the hazard when the detector alarms
Has to be sent for calibration meaning cover units are required (multiple sets)