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Regardless of the smoke ventilation method chosen, the control method and components are fairly universal.
Typically comprising an AOV control panel, manual switches, and in some cases smoke detectors.
AOV Control Panel
A modular unit will most often be used which provides a low voltage (24V) supply to the motor of the stairwell ventilator. The unit will include backup batteries to ensure it will continue to operate, even if there is a power failure. It will normally have a number of options for interfacing with remote systems and devices including:
- Fire alarm contacts for remote triggering in a small single-stair building
- Smoke detectors where needed, again normally in small single-stair buildings
- Thermostats for day-to-day ventilation
- Manual override switches
- Rain-sensing controls
- BMS or security systems to display system status
- AOVs or smoke shaft systems in lobbies.
It’s important that the control panel used is BS EN 12101-10 Smoke and heat control systems – Part 10: Power supplies, BS EN 12101-9 Smoke and heat control systems – Part 9: Control panels and ISO 21927-9 Smoke and heat control systems — Part 9: Specification for control equipment compliant.
Smoke Detector
Smoke detectors should comply with BS5839:1 and can be either an ionisation smoke detector or an optical smoke detector. Smoke detectors have a maximum coverage radius of 7.5m and should be overlapped to ensure there no blind spots.
Rain sensing controls
Wind sensors may also be incorporated into a stairwell ventilation system to prevent ventilators opening in high winds. The sensor should be located at a high level – it’s often situated on the ventilator for cabling purposes. It is then wired back to the control panel. They are overridden by emergency signals to ensure the ventilator opens regardless of the weather conditions.
Thermostats
Thermostats or temperature sensors can be used to cause the stairwell ventilator to open and close automatically. An upper and lower pre-programmed temperature will determine when the vent is opened. The thermostat should be tamperproof when located in a public area.
Override Switches
It is common practice to locate manual switches for firefighters to use at the entry and uppermost levels of a stairwell. These are required to override all other control modes to provide emergency access.