CEO, Firewize
07 Sep, 2022
A long hot shower is a wonderful experience especially if you're feeling a bit cold and want to warm up. Unfortunately the steam caused by a hot shower, hot running tap or even steam from a boiling kettle in a kitchen can activate a smoke detector.
For the sake of this article, steam is water in its gas phase and can occur due to boiling or evaporation and smoke is an aerosol or mixture of particulates (including steam) suspended in air.
In general terms a smoke detector operates on either the ionisation principle or the light scattering principle.
In both cases, steam can appear to a smoke detector as deceptive phenomena which can cause nuisance alarms.
Before we dig too deep into this article, we have to consider what areas of a building require the installation of a fire detector, notice we used the word fire detector, not heat or smoke detector? That's because a fire detector is the collective term to describe all types of fire detectors including heat detectors, smoke detectors, carbon-monoxide fire detectors and flame detectors.
The National Construction Code ("NCC") along with Australian Standard AS 1670.1 sets out the requirements for the selection and installation of fire detectors in buildings.
Clause 3.27 – Location of detectorsDetectors shall be provided throughout all areas of the building except as detailed in Clause 3.28 and where detection is installed in accordance with Clause 7.
Detection shall be installed in the locations specified in the NCC.
The Standard also specifies that photo-electric smoke detectors or carbon-monoxide fire detectors shall be installed in all sleeping areas.
Because we now know that steam is a leading cause of false alarms, we must design a fire detection and alarm system to eliminate or minimise the risk of steam as the cause of false alrms.
We can achieve this through a combination of factors such as design, mechanical ventilation and technology (in that order).
The design of a space that incorporates a source of steam such as a sole occupancy unit, nursing home room or hotel room will require the installation of a smoke detector or smoke alarm. The location of the smoke detector or smoke alarm should be such that it (1) complies with the requirements of the Standard and (2) is sufficiently far away from the source of the steam to eliminate the risk of false alarms.
The mechanical ventilation of a bathroom, kitchen or laundry (common areas where steam can accumulate) is necessary to extract the source of steam that can cause a false alarm. Ideally, mechanical ventilation should be arranged such that it operates automatically, either by sensing an increase in humidity or when the room is occupied. The mechanical ventilation should also operate for a sufficient time after the steam has been produced to eliminate the risk from a false alarm.
Most modern fire detection and alarm systems and fire detectors have features designed to reduce the incidence of false alarms. These features include, alarm verification and algorithms to overcome deceptive phenomena. While these are useful features, they are not a panacea for stopping all false alarms (but they do help).
