Gas Data GM25-4 Gas Analyser

Ground Gas, Borehole Flow & Contaminated Land Monitoring

The Gas Data GM25-4 is a professional portable gas analyser designed for site investigation, contaminated land assessment, landfill gas monitoring and environmental compliance. Its combination of gas concentration, pressure and low-flow measurement makes it particularly well suited to monitoring ground gas boreholes on greenfield and brownfield sites.

The GM25-4 provides six gas analysis channels, measuring methane (CH₄), carbon dioxide (CO₂), oxygen (O₂), hydrogen sulphide (H₂S), carbon monoxide (CO) and hexane (HEX). A PID correction factor is also provided for low-level VOC measurements, making the instrument particularly useful when investigating sites affected by hydrocarbons or other contamination.

In addition to gas composition, the GM25-4 measures atmospheric, static and differential pressure, together with bidirectional instantaneous and peak borehole flow. Unlike the GM25-3, which calculates higher extraction-system flows from differential pressure, the GM25-4 directly measures low borehole flow in litres per hour.

Key Features

• Six gas channels – CH₄, CO₂, O₂, H₂S, CO and HEX

• PID correction factor for low-level VOC measurement

• Atmospheric, static and differential pressure measurement

• Bidirectional borehole flow measurement

• Instantaneous and peak flow measurement

• Designed for low-flow monitoring in L/hr

• ATEX, IECEx and UKEx rated

• Compact handheld design

• High-contrast LCD display

• Internal data logging

• Instrument Connect software compatibility

• DataField GM25 Connect mobile app compatibility

• User-swappable rechargeable battery

• 8–12 hour typical battery life

• Optional vane anemometer for gas velocity

• Optional gas temperature probe

• 12-month service and calibration interval

Application Guidance

The GM25-4 is particularly suited to ground gas borehole monitoring where gas composition, borehole pressure and low gas flow need to be measured with a single instrument. Typical applications include contaminated land investigations, brownfield development, landfill perimeter monitoring, ground gas risk assessment and environmental compliance monitoring.