Maybe now the time is ripe to check on your smoke detectors or install some if you haven’t done so already – your home and your family need protecting, and in fact, some home insurance might be invalid without them.

There are several options available, the easiest being the ones you can buy in any hardware store, where you just add batteries and screw it up. Did you ever wonder how they work, or which one is the best option for you? To ensure the best possible result, there are one or two things to think about before you get your screwdriver out.

Different types

There are two types of smoke alarm - ionization or photoelectric, plus a ‘dual’ detector, which is a combination of the two.

Ionization smoke alarms are generally more responsive to flaming fires. These alarms have a small amount of radioactive material between two electrically charged plates, which ionizes the air and causes current to flow between the plates. When smoke enters the chamber, it disrupts the flow of ions, thus reducing the flow of current and activating the alarm.

Photoelectric smoke alarms are generally more responsive to fires that begin with a long period of smouldering fires. This type of alarm aims a light source into a sensing chamber at an angle away from the sensor. Smoke enters the chamber, reflecting light onto the light sensor, triggering the alarm.

Critical to safety

For each type of smoke alarm, the advantage it provides may be critical to life safety. Home fires, day or night, usually include a large number of smouldering fires and a large number of flaming fires, but you cannot predict the type of fire you might have in your home or when it will occur. Any smoke alarm technology must perform acceptably for both types of fires in order to provide early warning of fire at all times, and for best protection, it is recommended both (ionization and photoelectric) technologies be used in homes.

Although battery-operated smoke alarms, which usually use 9-volt batteries, are very popular due to their low costs and ease of installation, they only provide good protection if the batteries are checked and replaced on a regular basis. Apparently missing, disconnected, or dead batteries account for almost 75 percent of cases where a smoke alarm is present but does not operate properly, so check the batteries at least twice a year - replacing them each time the clocks change forward or back is a good reminder of when to do it. Most have a test button or an alarm to alert you when batteries need replacing as well.

New builds in many areas now require hard-wired smoke alarms that are interconnected, so that if one sensor detects smoke, all the detectors in the chain will sound loud alarms.


The proper positioning of smoke alarms is important.

It is recommended that alarms should be installed at least 3m from a cooking appliance to avoid false alarms when cooking, and they should be mounted high on walls or ceilings (remember, smoke rises), with wall-mounted alarms being installed not more than 30cm away from the ceiling. If you have ceilings that are pitched, install the alarm around 1m of the peak but not within the apex of the peak, and don’t install smoke alarms near windows, doors, or ducts where drafts might interfere with their operation, and however tempting, never paint or cover alarms with stickers or other decorations which could keep the alarms from working.

For optimum coverage, experts recommend installing smoke alarms inside each bedroom, outside each sleeping area, and on every level of the home, including the basement and near stairways. Garages are a very common source of fires, so they should be covered too if you have one, and even boiler rooms, laundry rooms or other utility spaces should be covered in your alarm plan. It is important that every floor of your home have at least one smoke detector at the very least.

It sounds a lot doesn’t it, but the devastating loss of your home - or family - is surely worth it.


Marilyn writes regularly for The Portugal News, and has lived in the Algarve for some years. A dog-lover, she has lived in Ireland, UK, Bermuda and the Isle of Man. 

Marilyn Sheridan