How Many Smoke Detectors Should I Have In My House?

According to figures released by the National Fire Protection Association, in 2018, the latest year for which figures are available, 2,720 civilians died in residential fires. That works out as an average of seven Americans dying in house fires every single day.

One of the most effective things you can do to minimize the risk of a house fire fatality is to ensure your home has enough working smoke alarms. But exactly how many smoke detectors should you have in your home?

How Many Smoke Detectors Should You Have In Your Home?

The number of smoke detectors you need in your home depends on the size of the building, how many floors you have, and how many bedrooms there are.

At the time of writing the National Fire Protection Association recommends the following:

  • One smoke detector in each bedroom.
  • An additional smoke detector in each hallway or area outside your bedrooms.
  • At least one smoke detector on each level of the home, without bedrooms, including the basement.

In addition, larger homes will benefit from snake detectors in each living space such as a den or study.

However, there is a lot more to effective smoke detector installation and use than the number of smoke detectors in your home. It is also important to know where to and where not to install your detectors, how to test and maintain your detectors, and when to replace them.

Where Should I Install Smoke Detectors?

When you install a smoke detector, whether it is in a room, a hallway, or any other part of your home you should, wherever possible mount the detector on the ceiling.

If it is not possible to place the smoke detector on the ceiling then it can go on the wall but it must be no more than 12 inches from the highest point of the ceiling. 

This is because smoke rises. If your smoke detector is too low on the wall, by the time the smoke reaches it and sets off the alarm, you may not have enough time to get out.

Just to make things a little more complicated, there is additional advice about where not to place your smoke detector.

Where Not To Install Your Smoke Detectors

Avoid mounting a smoke detector in the following areas:

  • Above or close to any cooking appliance.
  • In bathrooms, half baths, or showers. In fact anywhere that the air can regularly become damp or humid.
  • Any area that is excessively dusty such as an attic.
  • A garage.
  • Any area of your home where the air temperature falls below 40 degrees or reaches above 110 degrees on a regular basis.

The reasons for all of these exclusions are threefold.

  1. Heat, dust, grease, and humidity can all affect how well a smoke detector works.

    Having a smoke detector that you assume works, but is in fact not working correctly, may give a false sense of security. This is especially true if you only have one or two smoke detectors. As a result, a fire in your home may go undetected, just as it would if there were no smoke detectors at all.
  2. When a smoke detector goes off as a result of smokey cooking, or another non-fire related reason, some people may remove the battery to make it stop. The battery may be left out to avoid repeated false alarms or left out accidentally.

    In either case, you will be left with a non-functioning smoke detector.
  3. If you have a smoke detector that sounds false alarms or a regular, or semi-regular, basis you are more likely to assume that any alarm is a false alarm. As a result, you may fail to react quickly enough should the smoke detector sound in response to an actual fire.

    It is estimated that in a modern home, you have approximately two to three minutes to get out before you are overcome by smoke or flames so every second counts. Literally.

Smoke Detectors And Dead Air Space

Dead air space is the name given to the areas of a building where air does not circulate freely. Until recently the standard advice has been to avoid mounting a smoke detector in an area of dead space. The theory is that smoke may be slow to reach these areas resulting in a delay to the smoke detector sounding the alarm.

Research into how dead air space impacts the speed at which a smoke detector sounds has provided conflicting results. However, while there may be no advantage in avoiding dead air space when installing a smoke detector, there are no disadvantages.

As a result, avoiding dead air space is still appropriate when choosing where to place your smoke detector.

Smoke Detectors In The Basement

In most cases, it is best to place your smoke detector on the ceiling. However, the exception to this is when your smoke detector is in the basement. 

Do not install your smoke detector on the ceiling at the top of the stairs to your basement. It is possible that by the time any smoke reaches a detector at the top of the stairwell, a fire in the basement may have already spread up through the floor. 

As a result, smoke detectors should be mounted on either:

  1. The ceiling of the lower part of the basement
  2. The wall of the stairwell, approximately six feet from the ground level.

Smoke Detectors And Atypical Ceilings

Not every room has a uniform flat ceiling. Some homes have ceilings with recessed areas, others have ceilings that are pitched or otherwise atypical. In these rooms, there are additional considerations for the placement of smoke detectors.

Pitched Ceilings

In a room with a pitched ceiling do not put the smoke detector at the highest point. 

Instead, measure four inches down from the highest point, make a mark, and imagine a line drawn around the ceiling at this height. Then measure three feet from the highest point, make another mark and again imagine a line drawn around the ceiling at this height.

Your smoke detector should be installed in the zone between these two imaginary lines.

Recessed Ceilings

If at all possible, avoid installing a smoke detector in the recessed area of a ceiling. Instead, mount the detector in the lower part of the ceiling, or if that is not possible, on a wall no more than 12 inches lower than the ceiling height.

Other Installation Considerations

While it is not always possible to take all recommendations into account when choosing where to place your smoke detector, every effort should be made to stick to the following guidelines.


  • Smoke detectors installed on the ceiling should be placed no less than 12 inches from where the wall and ceiling meet. 
  • Do not put a smoke detector closer than 12 inches to the nearest light-fitting.
  • Leave at least 16 inches between a ceiling fan or air conditioning unit and your smoke detector. 
  • Wherever possible leave three feet between a bathroom door and a smoke detector.
  • Avoid windows, doors, air ducts, or anywhere else a draft may prevent smoke from reaching your smoke detector quickly.

How To Test Your Smoke Detectors

Test your smoke detectors once a month. It is a good idea to choose a specific date each month on which you will carry out the test.

First, let everyone know you are going to test the detectors. This will avoid anyone in your home panicking unnecessarily, carrying out the steps in your fire emergency plan, or calling fire rescue.

Next, get someone to stand as far away as possible from the smoke detector. They can tell you whether or not the detector can be heard clearly.

Finally, press the test button and hold it in. If the alarm sounds loud and clear your detector is working. If the alarm sounds but it is weak or inconsistent, replace the batteries and test again.

How To Maintain Your Smoke Detectors

Take a good look at your detector to ensure it is free from dust or other debris. If you can see any dirt, take the cover off and gently brush or vacuum the inside, replacing the cover, then carry out your test.

Even if the batteries in your smoke detector are working, replace them at least once a year. Many people choose to do this when the clocks go forward or back as this is a useful reminder.

Always test your smoke detector after taking off the cover and cleaning, or replacing the batteries.

When To Replace Your Smoke Detectors

The recommended lifespan of a smoke detector is ten years. That is not ten years from installation, but ten years from manufacture. The date of manufacture should be visible inside the smoke detector.

If you test your smoke detector and it does not work after you have tried two sets of batteries, replace it immediately.

You Can Never Have Too Many

These recommendations are for the minimum number of smoke detectors you should have in your home. Fewer detectors and you may not have enough coverage to provide effective protection in the case of a fire.



Geoff Southworth is the creator of, the site that helps new homeowners, investors, and homeowners-to-be successfully navigate the complex world of property ownership. Geoff is a real estate investor of 8 years has had experience as a manager of a debt-free, private real estate equity fund, as well as a Registered Nurse in Emergency Trauma and Cardiac Cath Lab Care. As a result, he has developed a unique “people first, business second” approach to real estate.

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