A device that normally holds a door open, but closes it automatically if any one of the following occurs.

• Smoke is detected by an automatic device of a suitable nature and quality in a suitable location.
• A hand-operated switch, fitted in a suitable position, is operated.
• The electricity supply to the device, apparatus or switch fails.
• The fire alarm system, if any, is operated.

A device which will allow a door held open by it to close automatically in the event of each or any one of the following:

• detection of smoke by automatic apparatus suitable in nature, quality and location;
• operation of a hand-operated switch fitted in a suitable position;
• failure of electricity supply to the device, apparatus or switch;
• operation of the fire alarm system if any.