How to determine if a flue damper is backflowing?

To determine whether a flue damper is experiencing backflow, we can observe and inspect the following aspects:

Observe airflow, pressure, and noise:

During normal operation of the flue damper, monitor whether airflow decreases, pressure drops, or abnormal noise occurs. These phenomena may indicate backflow issues.

Inspect the non-return valve:

The non-return valve is the critical component preventing grease fume backflow. Check whether grease contamination has caused sticking, preventing the valve from closing or opening properly. Should the non-return valve malfunction, it should be promptly cleaned or replaced.

Examine flue connections and return valve base:

Thoroughly inspect the flue connections, non-operational floor inlets, and damper bases for smoke leakage. Smoke escaping from these areas strongly suggests a backflow issue with the damper valve.

Possible Causes

Check Valve Malfunction:

As previously noted, grease buildup, damage, or improper installation of the check valve can prevent it from functioning correctly, leading to backflow.

Structural Construction Issues:

During building construction, failure to stagger the brickwork of adjacent exhaust outlets may create direct connections. Similarly, an excessively low exhaust outlet on the top floor without effective backflow prevention measures (such as installing a weather cap) can facilitate backflow.

Blocked Exhaust Ducts:

Accumulated dust or foreign objects within the exhaust duct may cause blockages, impeding smoke extraction and subsequently triggering backflow. Initial checks can be conducted using tools such as fine wire.

Addressing these potential causes, corresponding measures can be implemented to prevent and resolve backflow issues in flue dampers. These include: regular cleaning and maintenance of non-return valves, ensuring building construction complies with specifications, and conducting periodic inspections and clearances of exhaust ducts.