Which Gas Detector Do I Need
The right gas detector depends on three things: which gases could be present, how people are exposed, and whether the risk is in one place or moves with the worker. This guide walks through each decision and links to the detail.
Step 1: list the gases
Start from your COSHH assessment and, where flammable atmospheres may occur, your DSEAR assessment. List every gas or vapour that could be present and check each against its UK workplace exposure limit in our EH40 exposure limits reference. Oxygen depletion and flammable gas should be considered for any enclosed or below-ground space.
Step 2: choose the type
One known toxic gas, for example H2S at a pumping station or CO in a workshop: a single gas monitor.
Confined space entry: a pumped 4-gas monitor for LEL, O2, H2S and CO.
Several toxic gases, or a gas outside the standard four: a multigas monitor.
Solvents, fuels and VOCs: a PID; a benzene-specific PID for benzene.
A permanent risk in one area: fixed gas detection with a control panel and alarms.
Step 3: match the task
Utilities, sewers and telecoms chambers: pumped 4-gas monitors for entry, personal H2S monitors for operators. See confined space gas detection.
Water and wastewater treatment: H2S, methane, oxygen and chlorine. See wastewater gas detection.
Plant rooms, boiler houses and car parks: fixed CO or flammable gas detection. See CO detectors and LEL detectors.
Refrigeration and agriculture: ammonia and CO2. See ammonia detectors and CO2 detectors.
Tank cleaning and petrochemical work: LEL, O2, H2S, CO and a PID.
Step 4: disposable or serviceable
Maintenance-free disposable monitors run for two or three years with no calibration, only daily bump testing, and suit large fleets with one or two gases. Serviceable monitors take pumps and replacement sensors, last longer and usually cost less per year over their life.
Step 5: buy, lease or hire
Buy for everyday use. Hire for short projects and shutdowns, from £35 a week for single gas, £45 for 4-gas, £85 for multigas and £135 for a PID (excl. VAT). Whatever you choose, plan for calibration at the manufacturer's recommended interval (six months is common); we calibrate any brand from £40.
Still not sure?
Tell us the gases, the site and the task and we will recommend a model, set the alarms before dispatch and train your team if needed.
Talk to our engineers on 01489 326031 or email sales@7solutions.co.uk. We supply, hire, calibrate and train across the UK, Monday to Thursday 9am to 5pm and Friday 9am to 4pm.
Frequently asked questions
What is the most common gas detector?
For general site work and confined spaces, the 4-gas monitor measuring flammable gas (LEL), oxygen, hydrogen sulphide and carbon monoxide.
Do I need a pump on my gas detector?
Yes, if you test a confined space before entry. A pump draws a sample through tubing from inside the space so nobody has to lean in.
Can one detector cover every gas?
No. Each sensor measures a specific gas or group of gases. Choose sensors to match your risk assessment, and use a multigas monitor where you need more than four.
Disposable or serviceable?
Disposable monitors suit large fleets and one or two gases, with no calibration during their life. Serviceable monitors cost more up front but take pumps, replacement sensors and last longer.