| 摘要 |
<p>A ventilator (12) includes a vent (34) having at least a first, closed, state and an emergency, open, state and movable between them by actuators (57) under the control of a local controller (18). The actuators, for example electric motors, are powered solely by a local energy storage means, for example a battery, arranged to be recharged at a rate which is smaller than the rate of discharge when powering the actuators. A monitoring means determines if the energy in the energy storage means has fallen below a first threshold and provides a visual indication of this condition. The controller has a first control mode in which it is not able to move the ventilator (12) to the emergency state except in response to emergency commands, only, and a second control mode in which it is able to move the ventilator between the first state and the emergency mode in response to non-emergency commands to provide day-to-day ventilation, for example. The controller is moved to its first control mode if the battery charge level drops below a second predetermined threshold thereby preventing day-to-day ventilation but allowing opening of the ventilator in the event of a fire. <MATH></p> |
