Buildings on reclaimed land that contains domestic waste and rubble can be protected by an automatic gas monitoring system. It draws air samples from inside and beneath each building, analyses them for methane, carbon dioxide, hydrogen sulphide and oxygen, and raises an alarm to a central control point and a security company. This post explains how one was set up for a business park in Ireland, and what the system’s owners need to do for it to keep working.
The challenge: planning conditions on a reclaimed site
The business park stands on land reclaimed over roughly ten years, finishing in the mid-1970s. The fill was mostly builder’s rubble and domestic waste. Construction began in the mid-1990s and was done in two phases.
Planning conditions required gas control measures for every building. The engineers, architects and Organics met the local authority before construction started, to agree a monitoring design that would satisfy the conditions.
The approach: four parts per building
Each building has a purpose-built system with four main components.
1. A gas monitoring unit
The unit draws a representative air sample, filters out particles and passes it through in-line analysers:
- Methane and carbon dioxide by infra-red analysis.
- Hydrogen sulphide and oxygen by electrochemical cell.
A mechanical switching mechanism controls which sample is drawn, so samples from different points are not mixed. Results are converted to analogue and digital signals and shown as a percentage of gas in air on a local PC.
2. Sampling tubes and sensor heads
A representative number and spread of monitoring points were chosen for each building. A sensor head at each point connects to the unit through 8 mm internal diameter nylon tube. A purge pump in the unit pulls the samples through.
3. A hard-wired data cable
A seven-core cable runs from each unit to the central control station. It carries gas readings, faults and component failures in digital form.
4. Management software
Bespoke software controls purging, sampling and analysis, and presents the results in graphs and tables. Its main functions are:
- Comparing every reading against pre-set alarm levels.
- Raising alarms at the management suite, the security building and a 24-hour external security company.
- Warning of component failure.
- Triggering sounders and lights inside the affected building.
Why it works: monitoring plus a human response
The technology is only half the system. One management company has long-term responsibility for the gas control system. Organics trained its staff to read the results and to follow a set procedure when an alarm sounds.
If a building shows a high reading, the management company enters the building to check it with a portable hand-held gas analyser. Only if the reading is confirmed is the standard emergency plan put into action. That step stops a faulty sensor from causing an unnecessary evacuation, and it makes sure a genuine alarm is acted on.
Regular servicing keeps it reliable. The related service contract for this site schedules quarterly visits. See our post on what a gas equipment service contract should include.
What to consider for your own project
- Agree the design with the regulator early. Meeting the authority before construction avoids redesign.
- Monitor all four gases. Methane and carbon dioxide show gas; hydrogen sulphide is a toxic and odour risk; oxygen shows displacement.
- Choose the number of points deliberately. Sample points should represent the building, not just its corners.
- Give one party ownership. A single management organisation, trained and on call, keeps the response consistent.
- Plan for false alarms. A verification step using a portable analyser is part of the design, not an afterthought.
The Environment Agency’s landfill gas guidance is the starting point for gas risk in the UK.
FAQ
What gases should a building monitoring system measure?
Methane, carbon dioxide, hydrogen sulphide and oxygen are the four measured here. Together they show flammable gas, asphyxiant gas, toxic gas and oxygen depletion.
How does a system avoid mixing samples from different points?
A switching mechanism selects one sampling line at a time, and a purge pump clears the line first.
Who should respond to an alarm?
A trained management company. It checks the reading with a hand-held analyser and, if confirmed, follows its emergency plan.
Does a system like this need servicing?
Yes. Tubes, pumps, analysers and software all need regular inspection and calibration.
Need gas monitoring for a building?
Contact our engineers to discuss a monitoring system for your site.