thisplace.com.au - Smoke Alarms Save Lives

»	recently there has been loss of life as a result of homes not being fitted with smoke detectors
»	since July 1997, it's been mandatory for newly built homes to have electrically connected or hard wired smoke alarms
»	such alarm systems are also required to have battery back-up systems in place
»	older homes should have smoke alarms installed -these can be bought from most hardware stores as cheap battery operated units
»	all smoke detectors need to comply to the Australian Standard in both design and manufacture and in their installation

Two types of smoke alarms

Ionisation
these smoke alarms use a small amount of radioactive material to create electronically charged air molecules called ions - when smoke enters the chamber, it causes a change in the flow of ions triggering the alarm

Photoelectric
these smoke alarms contain a light source with a light beam, which is deflected by smoke into a photocell, thereby causing the alarm to activate

Smoke Alarms - some building tips

Queensland building laws require smoke alarms to be located between each area containing bedrooms and the remainder of the dwelling
the preferred location for these alarms is in the path that most people would take to evacuate the building
because smoke rises, alarms should be placed on the ceiling- where this is impractical, alarms should be placed high up on a wall
alarms generally, should not be placed at the apex of a cathedral ceiling, the corner junction of walls and ceilings and between exposed floor joists as these are common dead air spaces

Installation

normal flat ceiling or on exposed floor joists

install the smoke alarm a minimum of 500mm (20 inches) from the nearest wall - place the alarm in the middle of narrow hallways (ie less than 1 metre (39 inches) wide, passageways or corridors

high pitched ceilings

in rooms with high pitched ceilings (cathedral), mount the alarm near but not at the ceiling high point - the distance from the apex of a cathedral ceiling to the top of the alarm should be between 500mm (20 inches) and 1500mm (60 inches)

wall mounting

if mounting alarms on the wall, the recommended position is between 300mm (12 inches) and 500mm (20 inches)

windows, doors etc

smoke alarms should also not be installed too near a window, door, or the outlet of an air conditioner

Source: from the Building Services Authority for more details have at look at their website