Gas-management technology boosts building safety

Medem, gas safety
Protecting health and safety — Chris Dearden.

The Health & Safety Executive has warned those with a responsibility to maintain and service gas appliances in schools and other public buildings that they must have a robust gas safety management system in place. What does this mean in practice? Chris Dearden, managing director of Medem (UK), explains

A well thought out gas safety management system is essential to protect the occupants of a variety of buildings — including factories and schools. But what technology should you specify to maximise the system’s effectiveness?


There are, essentially, three technological weapons in the consultant’s armoury when specifying equipment to ensure a school or other public building has a robust gas safety management system in place.

• Gas detection


• CO2 monitoring


• Gas differential-pressure proving

Each weapon has its place in particular applications within the building, which could, for example, include laboratories, commercial kitchens or school classrooms.

Gas-detection systems can be used in boiler houses and plant rooms and are designed to enable boiler-house gas installations to meet the latest standards in the most effective and reliable way.

Gas detection involves connecting a number of low-voltage sensors natural gas, LPG or carbon monoxide to the control panel.

In the event of a high alarm from one of the sensors, the system will isolate the gas supply by closing a connected electric control valve. Emergency stop buttons can be fitted, and a fire alarm can close the gas valve when connected to the panel.

Typically, a liquid-crystal display (LCD) will show appropriate information about alarm situations and detector status etc.

Carbon dioxide (CO2) monitoring systems check the build-up of CO2 in a room. This is particularly important in school classrooms because high concentrations of CO2 affect the ability of children to learn. Building Bulletin 101 (BB101), a supporting document to the Building Regulations Part F, states that the maximum level of carbon dioxide in the air in a classroom should not exceed 1500 parts per million (PPM).

Medem, gas safety
Gas pressure proving is an important safety measure and can be linked with CO2 monitoring.

As a standalone system, a typical CO2 monitoring panel will indicate a pre-alarm at 900 ppm by means of visual indication on the panel fascia. The panel will indicate full alarm at 1400 ppm, again with visual indication on the panel.

A sounder is generally fitted within the panel. It is factory preset to silent but can be activated by means of jumper-plug adjustment where audible indication is required. The system will drop out of alarm condition as the carbon-dioxide level decreases, for example when windows have been opened or fans switched on to increase ventilation.

In the case of my own company’s products, a 5-year warranty is standard. In addition commissioning should not normally be required after installation as the sensor heads are pre-calibrated and factory tested.

Gas differential-pressure proving is designed for use where gas taps open to atmosphere are present in a gas line, such as in a laboratory. They can often also be used where an electronic control valve is incorporated within a gas supply to a building, so a pressure test can be carried out after the control valve has been closed.

These systems are designed for use in a wide variety of applications where key control of the gas supply and proving of the gas pressure in a gas line is required. Our own Medem GPPS-L, for example, is designed to protect people and property by testing for leaking gas each time the system is switched on. Whether gas is escaping from an open gas tap, an appliance that has been left on or from leaking pipework, the system will not open the gas solenoid valve should even the smallest leak be detected.

True gas differential-pressure proving (which has been patented by Medem UK) eliminates nuisance tripping of the gas supply which can occur with mechanical pressure switches and other methods that only monitor downstream of the control valve.

Gas pressure proving can also be combined with CO2 monitoring to ensure that all fans are running before gas can be used, conducting a gas pressure prove on the cook line and continually checking that the incoming gas pressure is sufficient and also monitoring carbon-dioxide level to ensure that Health & Safety Executive set levels are not exceeded.

The maximum allowed level of CO2 is 2800 ppm as published in HSE catering sheet 23 revision 1. At this level, the system will isolate the gas and advise the staff to ventilate the kitchen. Should the carbon-dioxide level rise above 2300 ppm, many of these systems incorporate an LCD in the panel to advise the staff to increase the speed of the ventilation fan.


Many of these systems incorporate self-diagnostics and can be connected to fire alarms and building-management systems.

Chris Dearden is managing director of Medem (UK).


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