Direct answer

On ESP optical sensors such as ALN-EN and ALN-EN(SCI), the optical sensitivity (1 %/m to 4.5 %/m) is adjusted from the loop view of an ESP control panel such as Latitude or an AP range panel or via the panel's configuartion software.ESP multi-sensors such as ACC-EN and ACC-EN(SCI) add a heat element whose threshold is adjustable from 0 °C to 88 °C, with 60 °C as the usual factory value. ALN-EN has no heat element, so only the optical sensitivity applies to it. Only the software setting changes — the physical sensor is not modified. Stay within the range covered by the detector's BS EN 54-5 or BS EN 54-7 approval: check the specification sheet for the exact ordering code before changing a value.

Applies to

Products / Models: ESP optical sensors ALN-EN, ALN-EN(SCI); ESP multi-sensors ACC-EN, ACC-EN(SCI); set from an ESP control panel (Latitude / AP range)
Firmware / Version: Latitude firmware EN-00.xx.Rxxx
Region: UK / Europe
Standards: BS EN 54-7 (point smoke detectors), BS EN 54-5 (point heat detectors); system design and log-book recording to BS 5839-1 in the UK

Why sensitivity and temperature settings may need adjustment

ESP panels (AP range, Latitude) re-calibrate every connected sensor once every 24 hours and apply drift compensation for contamination. The compensation range is bounded to — BS EN 54-7 and limits it so that the response value cannot exceed 1.6 times the initial value — and once a sensor exceeds its calibration limits the panel reports a calibration fault and the sensor has to be replaced. Drift compensation is not a substitute for the cleaning and servicing regime in BS 5839-1.
The sensor's fire point can also be adjusted manually to re-commission the device to better suit its environment (for example, a warehouse or kitchen).

Where to change settings (front-end steps)

Gain access to the device configuration settings at the panel.
Navigate to the loop and address of the device.
Open the device menu and edit the device attributes, or scroll to the sensitivity column.
Set the optical sensitivity value and the thermo/heat channel value within the ranges specified in steps 5 and 6 below.
For current ESP optical sensors such as ALN-EN and ALN-EN(SCI), the sensitivity levels are 1 %/m to 4.5 %/m, where the lower figure is the more sensitive setting. Check the specification sheet for the exact ordering code: the panel may not expose every level the sensor supports.
On ESP multi-sensors such as ACC-EN, the heat element can be adjusted from 0 °C to 88 °C, with 60 °C as the usual factory value. Note that the full software range is wider than the range covered by the EN 54-5 heat category marked on the device: raising the setting above that category takes the detector outside its approval.
Only part of the adjustment range is covered by the detector's EN 54 approval. Settings outside the range for which the manufacturer claims compliance take the detector outside BS EN 54-7 (smoke) or BS EN 54-5 (heat) and therefore outside the certification of the installed system. Confirm the approved range on the specification sheet for the exact ordering code before changing a value, and record the change in the system log book.
Adjust the values according to the site's fire risk assessment, and only after the other measures for limiting false alarms have been considered: detector type and siting, management of work in the protected area, and regular servicing. See How do I reduce false alarms on a fire alarm system?.
Save the changes and monitor the sensor to confirm the desired behaviour.

Notes and considerations

These settings are adjusted from the front-end panel or panel configuration software; the physical sensor hardware cannot be modified.
After making changes, observe the sensor for a period (trial) to ensure the adjustment reduces unwanted pre-alarms without compromising detection of real events.

When to contact technical support

The panel reports a calibration fault on the sensor after drift compensation.
Pre-alarms continue after the sensitivity or heat threshold has been adjusted within the approved range.
You are considering a setting outside the range covered by the sensor's EN 54 approval.

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

ALN-EN Specification, ISS7 / JUL25
ALN-EN(SCI) Specification, ISS5 / OCT24
ACC-EN Specification, ISS5 / JUL26
ACC-EN(SCI) Specification, ISS6 / APR24
ACC-EN Multi-Sensor Technology Guide, ISS4 / NOV20
HP900 PC Configuration Software Manual, Rev.0
AP Control Panel Range Product Manual, ISS1 / AUG13

Last reviewed: 2026-10-20 — Reviewed by: Hochiki Europe Technical Support

How do I change the sensitivity or heat threshold on an ALN-EN or ACC-EN sensor?

Optical sensitivity and heat thresholds are software settings changed at the panel; keep the new value inside the range covered by the sensor's EN 54 approval.