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Gas Detectors

7 Solutions supplies, hires and calibrates gas detectors for utilities, water companies, telecoms, ports, manufacturing and confined space teams across the UK. This guide explains the main types of gas detector, how to choose one for your hazard, and what you need to do to keep it compliant.

 

Portable gas detectors

  • Single gas detectors: small personal monitors for one known hazard such as H2S, CO or O2, including two and three-year disposables. Single gas monitors

  • 4-gas monitors: LEL, O2, H2S and CO in one unit, the standard for confined space entry. 4-gas monitor guide

  • Multigas detectors: five or six sensors, adding gases such as SO2, NO2, NH3, Cl2 or a PID. Multigas guide

  • PID / VOC monitors: photoionisation detectors for solvents, fuels and benzene. PID and VOC monitors

 

Fixed gas detection

Where a gas risk is permanent, in a plant room, boiler house, battery room, cold store or process area, fixed transmitters monitor around the clock and drive alarms, beacons and ventilation through a control panel. See our fixed gas detection systems guide.

 

Choosing by hazard

 

Buy, hire or lease

Buying makes sense for everyday use. Hiring suits short projects and occasional work, with weekly rates from £35 for a single gas detector, £45 for a 4-gas monitor, £85 for a multigas monitor and £135 for a PID (excl. VAT). Every hire unit is calibrated and supplied with a certificate. Gas detector hire

 

Staying compliant

  • Carry out a COSHH and, where flammable atmospheres may occur, a DSEAR risk assessment.

  • Set toxic alarms with the EH40 workplace exposure limits in mind.

  • Bump test before each day's use; calibrate at the manufacturer's interval, typically every six months.

  • Train users to read the display, respond to alarms and carry out daily checks.

 

Brands we supply and service

We are a Crowcon distributor and service centre, supply WatchGas and Honeywell instruments, and our engineers are trained to service Honeywell (BW and RAE), WatchGas, Dräger, Crowcon, MSA, Industrial Scientific, GMI, Oldham and more. Calibration is the same price for every brand: single gas £40, 4-gas £50, multigas £90, PID £140.

 

Electrochemical, catalytic, infrared and PID sensors

Most portable detectors combine several sensor technologies. Electrochemical cells measure toxic gases such as H2S, CO, SO2 and NH3, and oxygen, and typically last two to three years. Catalytic bead (pellistor) sensors measure flammable gases as % LEL but need oxygen to work and can be poisoned by silicones and lead compounds. Infrared sensors measure methane, other hydrocarbons and CO2 without poisoning but cannot see hydrogen. Photoionisation detectors (PIDs) measure VOCs at ppm and ppb levels.

Knowing which technology is inside your monitor matters: it decides what the detector can and cannot see, how long sensors last and what the calibration involves.

 

Exposure limits and alarm points

In the UK, workplace exposure limits for toxic gases are published by HSE in EH40/2005, usually as an 8-hour time-weighted average (TWA) and a 15-minute short-term exposure limit (STEL). Portable monitors normally have instantaneous, TWA and STEL alarms. Our EH40 reference for common gases lists the limits for the gases we detect most often.

 

Bump testing and calibration

A bump test exposes the detector briefly to a known gas to prove that the sensors respond and the alarms sound. It takes about a minute and should be done before each day's use. A full calibration adjusts each sensor against certified gas and is normally needed at least every six months, or sooner if a bump test fails, the monitor has been dropped or it has seen a high exposure.

Our calibration service covers any brand of portable or fixed detector at standard rates by instrument type: from £40 for a single gas monitor, £50 for a 4-gas monitor, £90 for a multigas monitor and £140 for a PID. Each instrument comes back with a traceable calibration certificate.

 

Training your team

A detector only protects people who know how to use it. Our gas detection training covers start-up checks, bump testing, reading alarms and what to do when one sounds. We run on-site courses anywhere in the UK from £750 a day, or a three-hour online session from £350.

Talk to our engineers on 01489 326031 or email sales@7solutions.co.uk. We supply, hire, calibrate and train across the UK.

 

Frequently asked questions

Which gas detector do I need?

Start with the hazard. One known toxic gas calls for a single gas detector; confined space entry needs a 4-gas monitor with a pump; several toxic gases or VOCs need a multigas or PID monitor; a permanent risk in one place needs fixed detection. Tell us the gases and the site and we will recommend a model.

Should I buy or hire a gas detector?

Hire suits short projects, shutdowns and occasional confined space work; from £35 a week for a single gas detector. If you need a detector for more than about three months a year, buying and servicing your own is usually cheaper.

How often do gas detectors need calibrating?

Most manufacturers specify a full calibration at least every six months, with a bump test before each day's use. We calibrate any brand from £40 per instrument.

Do you supply fixed gas detection systems?

Yes. We supply fixed transmitters, control panels and alarms to your specification, and service and calibrate installed systems on six-monthly or annual contracts.

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