Direct answer

On the FIRElink-25 and FIRElink-100 aspirating smoke detector, the exhaust must not be blocked or restricted while the detector is in operation. Remove the protective bung from the exhaust port before the detector is powered up. If the detector is mounted in a different air pressure zone from the area being sampled, pipe the exhaust back to the same air pressure zone as the sampling holes, using the piped exhaust docking station. FIRElink-25 and FIRElink-100 are not intended for applications with significant differences in airflow rate or pressure.

Applies to

Products / Models: FIRElink-25 and FIRElink-100 aspirating smoke detectors
Firmware / Version: All versions
Region: Not applicable
Standards: EN 54-20

Symptoms

Low flow or high flow faults that appear after installation, typically where the detector is mounted in a roof space, ceiling void or plant room and samples air from an enclosed or air-conditioned room.

Likely cause

A pressure difference between the area being sampled and the area where the detector exhausts causes this fault. FIRElink-25 and FIRElink-100 are not intended for applications with significant differences in airflow rate or pressure between these locations.

Resolution / Steps

Mount the detector on the piped exhaust docking station.
Fit the exhaust pipe into the exhaust port of the docking station.
Run the pipe back into the same air pressure zone as the sampling holes.
Remove the protective bung from the exhaust port before the detector is powered up.
Do not block or restrict the exhaust while the detector is in operation.

FIRElink-25 and FIRElink-100 use a low-power aspirator. Their installation manuals state that they are not intended to sample from areas with differences in airflow rate or pressure, and that such applications are not recommended. Piping the exhaust back corrects the pressure difference between the detector location and the sampled area; it does not make these detectors suitable for sampling across zones at different pressures. If the application involves significant airflow or pressure differences, contact Hochiki Europe Technical Support before designing the system.

When to contact technical support

If flow faults persist after the exhaust has been piped back, or if you are unsure whether the application is within the detector's design limits.

Safety note

This article is general guidance for Hochiki Europe products. Design, installation, commissioning, maintenance and modification of fire detection and alarm systems should be carried out by, or under the responsibility of, a competent person in accordance with the applicable standards (for example BS 5839-1 in the UK). Statutory requirements imposed by the relevant enforcing authority also apply. Always refer to the current product manual and data sheet for the exact model before carrying out any work.

References

FIRElink-25 Installation Manual (9-5-0-344, ISS5)
FIRElink-100 Installation Manual (9-5-0-345, ISS5)
Related: How do I download and install the Remote software for FIRElink aspirating detectors?

Last reviewed: 2026-10-21 — Reviewed by: Hochiki Europe Technical Support

Why does my FIRElink-25 or FIRElink-100 report a flow fault when it is mounted in a different air pressure zone?

The FIRElink-25 and FIRElink-100 exhaust must not be blocked; where the detector is in a different air pressure zone, pipe the exhaust back to the sampled area.