Where To Place Your Fixed Gas Sensors

By definition, your fixed gas sensors cannot be moved, so getting their placement right is key to creating the most effective gas detection system for your workplace.

Lack of Specific Standard For Gas Detectors

Unlike flame detection, there is no specific standard or guideline for gas sensors, only industry-approved best practices for locating, placement and number of gas detectors.

This is not surprising when you think of the complexity and speciality of gas detection; there are over 400 gases to possibly detect, with varied properties and environmental influences.

So how can we decide the number and placement of sensors needed for a specific environment?

Placement Based on Function

There are three main reasons why your environment needs gas detection: to protect the working environment itself, to monitor processes, or protect personnel. Each of these three functions will give an indication of how to place your sensors.

Workplace Protection

This means preventing damage to equipment within the area, or the building itself. Flammable gas detectors will fall into this category, requiring placement at the level the gas will settle at — being either heavier or lighter than air.

Process Monitoring

Gas detection systems involved in monitoring processes will be heavily influenced by the process itself — whether it’s monitoring ventilation control, or specific by-products of manufacturing processes. In order to get the best placement, you must understand the whole process, and work closely with your gas detection supplier to ensure the highest level of safety.

Personnel Protection

Positioning gas detectors to protect personnel comes down to understanding the normal operating zone for workers in that area. In this case, two detectors may be required; one set to monitor the processes that the personnel is working with, and another set to monitor the breathing zone.

Gas Sensor Placement Best Practices

Not all of these practices will be relevant to every environment; this should show you the importance of having clear and open communication with your supplier to ensure your detection system is working as efficiently as possible. In order to do this, you should:

1. Perform a potential gas hazard risk assessment for your environment.
2. Document the location and severity of all potential gas leak sites. This includes discharge points (where the gas is released from) and contact points (where the gas endangers equipment and personnel).
3. Investigate how these gases will behave. Is there specific airflow conditions or gas pockets that will influence how gas behaves in a location?

Do

• Place sensors as close as possible to potential gas leak sites.
• Place sensors where airflow is likely to produce the highest gas concentration or gas buildup. This includes corners or stopping points of gas-releasing moving devices.
• Place sensors relative to the target gases vapour density. Sensors should be located near the floor for gases or vapours three or four times heavier than air and near the ceiling or roof to detect lighter-than-air gases.

Don’t

• Don’t place sensors near entrances or fresh air vents, as sample concentrations will be diluted by incoming air.
• Don’t mount the detector on a surface subject to vibration as it could damage the detector. Anchor the detector to a wall or firm base rather than to a motor housing.

Factors to Consider

As with anything to do with gas detection, there is no ‘one size fits all’ approach. With this in mind, we’ve included some other factors to consider below.

Sensor Coverage

Like smoke detectors, a gas detector is capable of providing up to 75 square-metre area coverage with a 5-metre radius of operation. This can, of course, be influenced by many factors, including ventilation air flows, gas characteristics, equipment and the geometry of the room.

Control Panel Placement

Deciding where to position your control panel is just as important as sensor placement. It should be positioned outside of the hazardous area, while protected by connected gas detectors. They should be accessible so that when an alarm is triggered, personnel can evacuate the area and view the gas levels from the controller.

Audio-Visual Alarm Placement

If your detectors are protecting personnel in an area, the placement of audio-visual alarms is vitally important to alert them to a hazard.

It’s clear to see that there is a lot of consideration required to choose the right placement for your environment. DSA Suppliers has many years of experience in the gas detection industry and can help you throughout the whole process from choosing your selectors to installation and ongoing maintenance.