The Ventilation and Gas Detection Connection

Gas detectors may seem to sit inconspicuously on the wall just biding their time monitoring the air in the environment they've been put. But in actuality they are commonly active, triggering events and interacting with other systems in the building. In many applications, one of these systems is the ventilation equipment. Traditionally, ventilation exhaust fans and air-intake fans were operated continuously or on a cycle time basis. Not only was this expensive, but the wear and tear on the equipment led to a shorter lifespan and more maintenance costs. Fans range from a single fan with mechanical louvers all the way up to a large multi-fan system with variable frequency drives, N+1 redundancy, auto run, purge modes, etc. The commonality is they need power to run and they have inputs. In vehicle parking and maintenance facilities, the running of the engines in the enclosed space can lead to the build-up of hazardous to life levels of carbon monoxide. Gas detectors are mounted throughout the facility where they provide the best coverage of the area and are the first responders to the presence of the gas. They are configured with a low, medium and high alarm setpoints. So when the amount of carbon monoxide reaches the low alarm setpoint, the detector sends a signal to a controller. The controller activates a relay that starts the fan motor and turns the fan on half speed. The gas detector will stay in alarm and the fan will stay on until the gas level returns to a safe level. When healthy breathable air is present again, the gas detector sends a signal to the controller and the controller deactivates the relay and the fans slow down and stop. If there is enough carbon monoxide to reach the mid or high alarm setpoints the same process is followed but with increasing intensity such as additional fans would be turned on full speed, visual and audible alarms activated and probably the fire department or emergency response alerted. CET's gas detection equipment offers the following outputs to control various types of ventilation equipment:

• Dry contact relays, SPDT, rated for up to 5A @ 240VAC — up to a total of sixty (60) per FCS Controller
• Analog 4-20mA linear, 0-10VDC or 2-10VDC to the detected concentration of the target gas(es) - up to a total of sixty (60) per FCS Controller
• Modbus RTU communication directly via the WAN output on the FCS Controller
• BACnet MS/TP, BTL Labs approved communication directly via the WAN output on the FCS Controller The connection between the ventilation system and the gas detection system is an important one for reducing operating and maintenance costs and ensuring health and safety.

As gas detection experts, we know that the gas detection system controls the ventilation system so understanding how your ventilation system operates is as important to us as knowing your target gas!