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There are 4 gas detection product ranges, and even though a number of them can be used in a particular application, there is probably one that would be a better fit.

When selecting the gas detection  product for your installation, consider the following:

a-What gas / gases need to be detected

Different sensor technologies will be used to detect different gases at different levels (a compressive list of gases by sensor Technology can be found in the FAQ question 5 or in the gases section of the website).

b- What is the purpose of the system – personal safety, compliance with Ex regulations / zoning or for gas detection standards

You need to use a sensor type suited to the gas and capable of detecting at the levels required. OEL levels are generally lower than those specified in other standards.

Generally for toxic gas applications the OELs are low and you need electrochemical sensors to work at such low levels (typical gases include Ozone, Chlorine, Hydrogen Sulphide, Carbon Monoxide, Oxygen, Ammonia, etc.).

Normal industry practise has resulted in typical gas detection ranges for different purposes and these are established nationally by the appropriate safety agency with reference to international norms such as MAK (Germany) AGCIH/OSHA (USA) HSE (UK).

c- Number of sensor required

There is no legal guideline on sensor coverage. The British Standard that preceded EN378 specified 36m² per sensor in a machinery room. This can be increased if there is a discernible airflow.

In refrigerated spaces e.g. cold store with evaporators, coverage can be increased to 50/100 m² due to the strong air movement. In car parks with ventilation we suggest 50/100 m².

What criteria do you use to make a decision on a gas detection solution?

1- Determine how many sensors are needed

MGD goes up to 6 but you can use a number of MGD Panels.  IAM, MGS and ST-IAM are unlimited.

2- Do you want a set point system?

MGD, IAM are preset alarm systems.  The MGS and ST-IAM have linear analogue outputs for continuous monitoring and reporting.

3- What level of detection and what gas is to be detected?

Electrochemical and catalytic sensors are available with MGS and ST-IAM sensor and so if you need these sensors for the gas in question only use these models. Very low levels of detection are not suited to semiconductor or catalytic sensors

MGD uses semiconductor (SC), and infrared (IR) for CO2.  The IAM uses SC.  The MGS uses SC, EC and IR. The ST-IAM uses all sensors: SC, catalytic (CAT), electrochemical (EC), and IR for CO2.

4- Are visual or audible alarms required?

MGD, IAM and MGS have warning lights, sounder and relays for connection to other systems. The MGS and ST-IAM have linear outputs and relays.

5- How to detect different gases in the same installation?

You can mix sensors for different levels of alarm and gases on the MGD 2 level systems and on the ST-MON and the IAM-C panel.

6- What is the Power supply required?

The MGD and IAM operate on mains 230V/120V.

The MGS and ST-IAM operates on 12/24 Vac or 12/30 DC.  The ST-MON panel operates on mains 230V/120V.

7- Any special requirements for sensor enclosure?

EExd explosion proof, IP65/IP66 enhanced protection, Low Temperature, duct mount, vent pipe, remote sensor, are all available in the MGD, MGS and ST-IAM ranges.  IAM is not available in most optional housings.

8- Do you need a ST-MON panel?

This can take up to 99 sensors with one level of alarm on the RS485. It has audible, visual alarms, 2 relays, and data storage.

PRODUCT COMPARISON TABLE

Download the PDF – FAQ 6. How to select the appropriate Murco product?

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