Smoke Alarms

Save your life, Protect your property, Reduce the damage to personal property

Smoke alarms are devices that detect smoke and sound an alarm. Smoke alarms alert and wake people allowing valuable time to get out of a house during a fire. When you go to sleep, your sense of smell also goes to sleep. If there is a fire, toxic fumes may overcome you before you wake up. Smoke alarms should not be confused with smoke detectors, which are devices without an audible alarm function. These are generally used in commercial premises.

From 1 July 2007, owners of all houses and units in Queensland must install at least one 9 volt battery powered

Smoke alarm.

As a legal minimum requirement, a smoke alarm must be installed on or near the ceiling on any storey:

- Between any area containing bedrooms and the rest of the house or unit e.g. hallways; or

- On a storey not containing bedrooms on the most likely evacuation route from the storey.

Current Building Code of Australia (BCA) Law for New Homes, Units and Renovations

Since 1 July 1997 in Queensland, it has been mandatory under the BCA to have hard-wired (240 volt) smoke

alarms be installed in residential homes built or significantly renovated (more than 50%) after this date. These alarms must meet all requirements of Australian Standard (AS) 3786, and the BCA specifies location requirements for smoke alarms.

Minimum Requirements

The minimum required is a 9 volt, battery powered smoke alarm, in which the battery requires replacement annually. It is estimated that the laws will require the typical home to install one or two alarms.

There are a number of ways in which smoke alarms can be powered, these include:

9 volt batteries that have at least a one year life and require changing each year
Long-life 9 volt lithium batteries that can be renewable or non-removable that last the life of the alarm, up to 10 years. These avoid the need for the householder to replace the battery annually. In some models the battery cannot be removed due the unit being sealed; and
Mains power supply, with some models featuring a rechargeable battery back-up. Often called hard-wired (240 volt) smoke alarms, these offer the highest level of reliability, but must be installed by a licensed electrician. Some smoke alarm models can be connected in groups so that if one alarm goes off it will also set off others. This will require the work of an electrician.

Types of Smoke Alarms

There are two types of smoke alarms - ionisation and photoelectric. Ionisation smoke alarms mainly detect the

presence of extremely small particles of smoke, whilst photoelectric mainly detect visible smoke. The type most

commonly installed in homes has been the ionisation smoke alarm.

Ionization Detectors
Ionization smoke detectors have an ionization chamber and a source of ionizing radiation. The source of ionizing radiation is a minute quantity of americium-241 (perhaps 1/5000th of a gram), which is a source of alpha particles (helium nuclei). The ionization chamber consists of two plates separated by about a centimetre. The battery applies a voltage to the plates, charging one plate positive and the other plate negative. Alpha particles constantly released by the americium knock electrons off of the atoms in the air, ionizing the oxygen and nitrogen atoms in the chamber. The positively-charged oxygen and nitrogen atoms are attracted to the negative plate and the electrons are attracted to the positive plate, generating a small, continuous electric current. When smoke enters the ionization chamber, the smoke particles attach to the ions and neutralize them, so they do not reach the plate. The drop in current between the plates triggers the alarm.

Photoelectric Detectors
In one type of photoelectric device, smoke can block a light beam. In this case, the reduction in light reaching a photocell sets off the alarm. In the most common type of photoelectric unit, however, light is scattered by smoke particles onto a photocell, initiating an alarm. In this type of detector there is a T-shaped chamber with a light-emitting diode (LED) that shoots a beam of light across the horizontal bar of the T. A photocell, positioned at the bottom of the vertical base of the T, generates a current when it is exposed to light. Under smoke-free conditions, the light beam crosses the top of the T in an uninterrupted straight line, not striking the photocell positioned at a right angle below the beam. When smoke is present, the light is scattered by smoke particles, and some of the light is directed down the vertical part of the T to strike the photocell. When sufficient light hits the cell, the current triggers the alarm.

Recommendations Above Minimum Requirements

Your protection against fire increases with the quality and type of smoke alarm that is installed. Research indicates that photoelectric smoke alarms are generally more effective than ionisation types across a wider range of fires experienced in homes. For this reason, QFRS recommends that photoelectric smoke alarms be installed, especially if you are installing only one alarm. If you already have smoke alarms installed, QFRS recommends that you supplement the existing alarms with photoelectric types, especially between sleeping areas and exits from your home (e.g. hallways); and at the end of the service life of existing smoke alarms, replace them with photoelectric types.

(Click the following for more information)

How Do I get Smoke Alarms

Choosing Smoke Alarms

Installing & Positioning of Smoke Alarms

Maintaining Smoke Alarms

How many Smoke Alarms do I require by Law

HOW DO I GET SMOKE ALARMS

Many hardware, home supply or general merchandise stores carry smoke alarms. Prices vary depending on brands, types and features.

CHOOSING SMOKE ALARMS

How to choose between brands
There is no general-purpose smoke alarm for all locations. The correct choice is important to avoid false alarms, as excessive false alarms can lead to the householder disabling the smoke alarm.

There are two choices of smoke alarms:

240 Volt Smoke Alarms (Also called hard-wired smoke alarms)
A 240 volt smoke alarm is connected to a home's electrical system and has battery back-up power supply.

Advantages

Considered more reliable in the longer term
Early warning - occupants alerted in the shortest possible time
Uses a battery to provide back-up power if the AC power fails
Models can be interconnected which sound alarms in all connected units
Can come with a long life Lithium Battery - built-in and tamper proof
Power-on indicator
In some models a hush button - to stop nuisance alarms
Test button - to ensure correct operation
Tested by Scientific Services Laboratories to comply with AS3786
Some can be purchased with a rechargeable battery (non-replaceable)

Disadvantages

More expensive
Need to be installed by a qualified electrician

9 Volt Smoke Alarms (Also called battery operated smoke alarms)
A 9 volt smoke alarm is stand alone and operated only by a battery.

Advantages

Easy to install
Test button - to ensure correct operation
Low battery indication
In some models a hush button - to stop nuisance alarms
Battery missing indicator
Tested by Scientific Services Laboratories to comply with AS3786
Some models can be interconnected

Disadvantages

Battery needs to be replaced regularly

Smoke alarms can be installed either stand alone or interconnected. Interconnection allows all smoke alarms to sound simultaneously should any one alarm activate. All occupants are alerted, maximising the opportunity for escape. Children's bedrooms should have a smoke alarm, and be connected to the parent's bedroom because children sleep much sounder than adults. A significant percentage of residences fitted with smoke alarms remain unprotected due to depleted or missing batteries.

The installation of smoke alarms in new residential properties became compulsory in Queensland in 1997. The ‘Standard Building Regulation 1993' outlines that in Queensland, hardwired smoke alarms are required to be installed in all new properties and those properties that are being significantly renovated (i.e. renovations exceeding more than 50 percent of the original building, measured over the roof and the external walls).
(Building Code of Australia, 1996 Vol.2 3.7.2).

Generally, there are two kinds of smoke alarms - ionisation and photoelectric.

Ionisation Smoke Alarms
They ‘smell' the smoke. This type detects invisible particles of combustion e.g. from cooking toast. They activate more quickly for fast, flaming fires and little visible smoke.

Advantages

Cheaper than other types
Very good with fast flaming fires with little visible smoke
Suitable for general use
Less prone to false alarms due to dust and steam

Disadvantages

Very susceptible to nuisance alarms due to cooking
May be slow to respond to slow smouldering fires
Contain radioactive material

Photoelectric Smoke Alarms (also known as optical)
These ‘see' the smoke (optical). This type detects visible particles of combustion e.g. smouldering cigarette smoke. They respond to a wide range of fires, but they are particularly responsive to smouldering fires and the dense smoke given off by foam filled furnishings or overheated PVC wiring.

Advantages

Good for smouldering fire and dense smoke
Not as prone to cooking nuisance alarms
Contain no radioactive material
Suitable for general use

Disadvantages

Prone to nuisance alarms from dust and insects - must be kept clean
More expensive

It is expected that stocks of photoelectric alarms will become more readily available at retailers as demand increases.

Other Smoke Alarm Options

Alarms for the hearing-impaired
Alarms with emergency lights
Special models for kitchens and caravans
Inter-connectable models that sound alarms in all connected units

What to look for?
Queensland Fire & Rescue Service recommends you buy an alarm which carries the Standards Australia Mark or is Scientific Services Laboratory (SSL) labeled. According to legislation smoke alarms installed must comply with AS 3786-1993. Despite this requirements, some smoke alarms that do not meet the Standard are still available in some stores. The Office of Fair Trading have confirmed that the sale of these is not against the law.

QFRS strongly recommends, when purchasing smoke alarms, people check that the smoke alarm they are buying complies with the Standard. The following labels will appear when smoke alarms complying with AS 3786-1993 are purchased.

INSTALLING & POSITIONING OF SMOKE ALARMS

Smoke rises therefore smoke alarms should be placed on the ceiling. If that is not possible, it may be positioned high on a wall, according to the manufacturer instructions.
New smoke alarm laws require owners of all homes and units (Class 1a and sole occupancy units in class 2 buildings) to install and maintain smoke alarms in all older (pre 1997) homes by 1 July 2007.

As a legal minimum requirement, a smoke alarm must be installed on or near the ceiling on any storey:

Between any area containing bedrooms and the rest of the house or unit e.g. hallways;
On a storey not containing bedrooms on the most likely evacuation route from the storey.

The Queensland Fire and Rescue Services strongly recommend that you consider installing additional alarms. In cases where occupants sleep with the door closed, it is especially recommended that an alarm be installed in each bedroom.

Since July 1997, mains-wired smoke alarms have been required in all new and significantly renovated homes and units built after this date. These need to be installed by a licensed electrician, in line with BCA standards.

To maximise smoke alarm operation avoid installation in the following positions:

In dead air space. This is an area in which trapped hot air will prevent smoke from reaching the alarm. This space generally occurs at the apex of cathedral ceilings, the corner junction of walls and ceilings, and between exposed floor joists
Near windows, doors, fans or air conditioners. Excessive air movement may prevent smoke and gases from reaching the smoke alarm or cause nuisance alarms
In or outside of the bathroom as steam may cause nuisance alarms
Closer than 1.5 meters to fluorescent fittings as electrical ‘noise' or flicker may affect the smoke alarm
In kitchens. If there is no alternative, a photoelectric type is preferred
In insect infested areas, as insects flying into the alarm could cause nuisance alarms

MAINTAINING SMOKE ALARMS

How do I keep my smoke alarms working?
Smoke alarms can only save lives if they work properly, and are properly taken care of.

Steps to remember:

Once a month you should check the battery by pressing the test button. If you cannot reach the button easily, use a broom handle
Keep them clean. Dust and debris can interfere with their operation, so vacuum over and around your smoke alarm regularly
Replace the batteries at least once a year. Pick a public holiday or your birthday and replace the batteries each year on that day. In most models when batteries are low the detector will sound a short ‘BEEP' every minute or so. This is your reminder to replace the batteries
Smoke alarms must never be painted
If cooking and smoke sets off the alarm, do not disable it. Turn on the range fan, open a window or wave a towel near the alarm
Do not remove the batteries from your smoke alarm
Smoke alarms wear out over time. They should be replaced prior to the expiry date on the manufacturer's warranty. You may want to write the purchase date with a marker on the inside of the smoke alarm unit. That way, you'll know when to replace it
Read the manufacturer instructions

* All types of smoke alarms have a limited life-span and need to be replaced according to manufacturer's instructions.

HOW MANY SMOKE ALARMS DO I REQUIRE BY LAW

Every residence is different and you will need to assess your home. The following is suggested as a guide.

Alternatively, follow the manufacturer's instructions:

A smoke alarm outside each sleeping area and on each level of the home provides a minimum degree of protection from the threat of fire;
In a single-level home, one alarm may be sufficient (as a minimum) if all the bedrooms connect to a common Hallway;
Additional alarms are needed in homes with separated sleeping areas;

Where occupants sleep with bedroom doors closed, install a smoke alarm in each bedroom and the hallway.