Everything You Need About Heat Detectors

Everything You Need to Know About Heat Detectors

Table of Contents

There are many dangers in the world today. Anything can happen when it comes to hazards that you face in life. One such thing that can cause a lot of problems is a fire. A fire can absolutely destroy a person’s life, whether they lose their home, business, or even a loved one. Fortunately, there are ways that you can detect fire and high temperatures before they happen with heat detectors and smoke detectors. If you want to know all about heat detectors and how heat detectors work, we have the information for you.

These temperature and impurity detectors can save your life. In the US, every day, there are 7 people who die in fires on average. These fires can happen in many ways, so it is extremely important to have some sort of fire detector in your home. Not only can it save your life, but it can save your home, too. Calling the fire department in a matter of a few seconds can save a lot more than you think. Even an additional second of a fire can lead to more destroyed things. The sooner you get the fire put out, the more things you can save from the fire.

What Is A Heat Detector?

A heat detector is a device that does just that—it detects heat. However, there is a lot more to it than just detecting heat. You might wonder if these heat detectors are the same thing as a smoke detector. It’s not, but we get into more detail on that further down. Heat detectors are fire alarms that activates when the convected thermal energy (heat transfer due to bulk movements of molecules) of a fire increases the temperature around the alarm.

Of course, that’s just a fancy way of saying “it beeps loudly when it gets really hot very quickly.” There are two different types of heat detectors. These are:

  • Fixed Temperature
  • Rate-of-Rise (ROR)

We’ll get into the specific types further in this article, but normally, you’ll be using a fixed temperature heat detector in your home or business. Keep in mind, however, that heat detectors are not meant to replace smoke detectors completely. Smoke detectors are a much better way of detecting a fire faster than a heat detector, despite smoke detectors sometimes giving false-positives. Heat detectors are useful in the kitchen and for water-activation devices. Heat detectors are more about protecting property, not life.

Additionally, heat detectors can come in two different types of area detection. It can either be:

  • Spot
  • Linear

These two types are different in the sense of area it is measuring. A spot type detector will have one location in the building or home. A linear heat detection will spread out over a larger physical area, but is usually more appropriate for bigger buildings.

How Do Heat Detectors Work?

The thing that makes heat detectors different from other things is that it measures the amount of molecules in the air around it. Heat detectors were first invented the early 1900s and have been in development ever since. There are many technologies that have come about since then. There are four types of technologies that are used when it comes to heat detecting:

  • Electromechanical – A combination of mechanical movement to activate an electrical circuit
  • Optomechanical – Uses fibre optic cables which are surrounded by a heat-sensitive covering.
  • Electronic – Uses a thermistor, which is an electrical resistor whose resistance is reduced by heating, which has its resistance change depending on the temperature
  • Electropneumatic – Uses different pressures from the change in temperature, which is released through a vent and activates the alarm in the process.

While each of these types of heat detectors will do the job, that doesn’t necessarily mean one is better than the other. Each type of technology will do what you expect them to do, and that is to sense heat whenever there is a rapid increase in temperature. Again, it shouldn’t be treated as a life preserving device like a smoke detector, but it is still a useful tool to use in your kitchen.

How Do Rate of Rise Heat Detectors Work?

When it comes to rate-of-rise (ROR) heat detectors, they operate a bit differently from fixed temperature heat detectors. Where fixed heat detectors have a single temperature (usually 136.4 F) they recognize going past, rate-of-rise heat detectors will detect a rapid increase. Fixed temperature heat detectors are usually the most common, but rate of rise detectors are becoming more popular.

With a rate of rise heat detector, it will recognize whenever there is a fire. However, slow-rising fires may not be picked up by it. With its two heat-sensitive thermocouples or thermistors, it will be able to pick up the molecules moving at a rapid pace. Since it doesn’t detect all types of fires, it is usually combined with fixed temperature heat detectors.

Some heat detectors have both types of detection in them. Many fixed-temperature designs will include a rate-of-rise technology, so you don’t usually have to choose between them if you want to keep your property safe. Depending on the situation, you might get more than one, but a heat detector will let you know that a fire is happening.

Do Smoke Detectors Detect Heat?

To put it simply, smoke detectors do not detect heat. Even if you put heat near a smoke detector, it will likely not activate at all. There are different types of smoke detectors, but both types deal with something in common: they have beams that are broken by smoke. Whenever smoke wafts into the smoke detector, that smoke will break the beam and cause the alarm to trigger. Since heat is not a visible thing, it will not cause a smoke detector to activate.

Whenever it comes to smoke detectors, it can be either of these types:

  • Ionization
  • Photoelectric

Both types come with a beam inside, as said above. An ionization smoke detector uses ionizing radiation to find smoke in your home. It is the better of the two at detecting small amounts of smoke, along with being inexpensive. It has two plates inside of it which emit an active source of ionizing radiation. Because smoke has a slight electrical current, it will activate the alarm because of its reaction with the radiation.

Photoelectric smoke detectors are slightly less complicated. These smoke detectors allow light to pass through a small beam. Whenever the smoke goes through it, the light will bounce off the particles and scatter the light, which will then hit the sensor in the smoke detector. This will cause the alarm to trigger, beeping loudly to alert you that there may be smoke in the house.

Because of this, there are a few times when a smoke alarm may go off when there is no fire. Whenever you’re cooking or warming up food, it might emit a bit of smoke. The smoke detector may pick this up and start going off. Thankfully, it only takes a little while to reset, but it’s better for it to work than not! If you find that your smoke detector is giving off a false-positive alarm, waving a sheet or pillow against it will likely clear out the smoke.

Do I Need A Heat Detector In My House?

In older homes, smoke and heat detectors are recommended to be put up, but aren’t legally required. However, some states require new establishments to have a smoke detector and heat detector. Depending on the size of the home or building, they may require more than one. If you’re having a home or business built, it might be a good idea to ask your contractor about them.

Even if law does not require you to get a heat detector, it is a good idea to get a heat detector and smoke detector. These two devices can save your life in the case of a fire. Not only that, but it can save your home, too. Fires will destroy anything that it touches and the longer it rages, the more things will fall to its flames. You never want to let it go if you can help it, so a heat detector and smoke detector can save a lot.

It may not be required by law in some cases, but it is a wise thing to get these devices installed in your house. You should have at least one smoke detector in each room of the home, especially ones prone to using heat. This is especially true for the kitchen, considering smokeless fires can happen, which is where heat detectors come into play. They are relatively inexpensive, so don’t skip out on them.

What Temperature Does A Heat Detector Need To Activate?

Since there are two different main types of heat detectors, the answer to this question can vary slightly. Both types of heat detectors will do things at different temperatures. When it comes to these, the temperatures are as follows:

Fixed Temperature Heat Detectors

Each heat detector has a specific temperature it picks up. Fixed temperature heat detectors have a set one that it recognizes before it sets off its alarm. This temperature is either 135°F (57°C) or 194°F (90°C). Depending on what type of building you’ll use it for, you will likely come across the 135 F more often. The higher of the two are used more often by business dealing with welding or steel works.

Rate-of-Rise Heat Detector

Rate of rise heat detectors do something differently than fixed temperatures. While this type of heat detector won’t activate at a certain temperature, it will activate at a specific increase in temperature. These devices will recognize when temperature increases of around 12° to 15°F (6.7° to 8.3°C) in a matter of a minute. It doesn’t matter where the temperature started. If the temperature rises that quickly, there is most likely a problem.

Where Should Heat Detectors Be Placed?

A heat detector is not like a smoke detector. While smoke detectors will be more plentiful through a home, a heat detector is only really necessary in a couple of rooms. A good rule of thumb to consider is the level of smoke or fumes where these rooms are. This is because things like dust, smoke, and other particles in the air can set off a smoke detector with ease.

Either way, you should put a heat detector wherever you think a fire could break out. Some fires don’t produce smoke immediately, so a heat detector may be better in some cases. These are some of the most common spots to put them:

  • Kitchen
  • Garage
  • Attic or Loft

The kitchen is obviously a no-brainer. If there’s a fire in the home, one of the most common spots that it happened is the kitchen. Considering that we use heat to cook our food, a fire has a chance of happening. A piece of food might catch on fire, oil might get too hot, or even an oven burner could short out.  There are so many ways that a fire can start in the kitchen that it’s a good idea to have both a heat detector and smoke detector in the kitchen.

As for garages and attics, there are a lot of fumes and dust that can happen in these areas. Because of this, smoke detectors might malfunction or give off false-positives of detecting smoke. Dust can cause the sensors to become clogged or even broken, so a heat detector is a good choice to avoid this. When you have a heat detector, the dust won’t matter.

Where Are Heat Detectors Required?

There are a few areas in the home that should have heat detectors. Some are better than others. Are heat detectors required in kitchens? As said above, it depends entirely on the state that you live in. Normally, older homes won’t have to put up a new heat detector or smoke detector. However, some landlords require it, so you may have to have them regardless. New buildings may require multiple fire detectors placed about.

You should have multiples of these detectors in your home. The kitchen is the best place for them, considering that fires often happen in the kitchen. You don’t want to let it get out of control. Some fires don’t have a lot of smoke, so high flame fires can set these heat detectors off. Heat detectors aren’t required to be put up, but it is certainly something that you should have in your home. However, your landlord may have you contractually obligated to keep them up and in working order or to alert them whenever the batteries are dying.

Do Heat Detectors Need To Be Replaced?

To start off, heat detectors do not usually need batteries. There are a couple of devices that do require batteries, especially if the heat detector is combined with another device. For example, there are smoke detectors and heat detector combos. Since heat detectors do not normally use batteries, they will simply work whenever the necessary things happen. That is, if heat increases rapidly or the temperature reaches the fixed threshold.

Heat detectors do need to eventually be replaced, though. Normally, heat detectors can last up to ten years whenever operating. This means it can work through over 87,000 hours. It is a good idea to test them now and then, though. Heat detectors won’t normally alert you if they’re starting to malfunction like smoke detectors do with low batteries. If you want to learn how to test these heat detectors, there is more information below.

How to Tell The Difference Between Heat And Smoke Detectors

The biggest difference between a heat detector and a smoke detector are their primary functions. A heat detector will measure a rise in temperature, while a smoke detector will detect smoke in the area. Visibly, it might be a bit difficult to see a difference between them when they’re on the ceiling. If you or your landlord doesn’t know what kinds of devices are installed in your home, a simple test can determine what they are.

Most smoke detectors have a test button on it. It is one of the only defining features that you can see between a smoke detector and heat detector. On the smoke detector, pressing the button after a few seconds should result in a very loud siren to come from it. If that is the case, then your smoke detector should be fine. Heat detectors usually don’t have these sorts of test buttons, so continue reading to find out how to test one. Below are ways to test a fixed temperature heat detector.

How to Test Fixed Temperature Heat Detectors

Using a heat gun, hair dryer, or heat lamp, all you have to do is simply activate it around the device in question. Keep in mind that you shouldn’t increase the temperature by more than 100F (55C) of the unit. Otherwise, it can cause a change in the fixed temperature. You don’t want to break your heat detector while testing it, so be sure to stop whenever you hear the alarm that the heat detector has.

This can also be done with a rate of rise heat detector as well. Letting the hair dryer heat up before you start applying it to the rate of rise heat detector is a good way to test it, but again, don’t let it sit for too long. Once the alarm starts, remove the source of heat immediately. The hair dryer should increase the heat quickly enough to activate the heat detector.

How Many Types of Heat Detectors Are There?

There are mainly two types of heat detectors on the market. Some brands combine both a heat detector and smoke detector, but that doesn’t necessarily make them better. Each heat detector and smoke detector has different things that they can do. Both types of heat detectors work as well as the other, it simply depends on what is available to you. The two types of heat detectors are:

  • Fixed Temperature
  • Rate of Rise

As said above, these two heat detectors have very specific things that they do. A fixed temperature heat detector will alert you when there is a temperature that goes above the threshold. A rate of rise heat detector will tell if there is a rapid increase in temperature in the vicinity it is placed. Both of these are good things to have in your home.


Heat detectors are an important thing to prevent damage to your home or business. It usually isn’t required to have one, but it can be beneficial in the long run. At the same time, heat detectors should not be a replacement for smoke detectors, since they are not a life-saving device. They are more beneficial to saving property. However, having both a smoke detector and heat detector can help you recognize a fire even faster.

Some new establishments may require you to get a heat detector or smoke detector. Landlords may also require you to have working smoke and heat detectors as well. If they start beeping because of low batteries, you should alert your landlord immediately if you can’t change it yourself. Some brands combine these types of detectors, so you should get one that works for you.

People use heat detectors in areas where smoke detectors may not function fully. For example, they can be used in the kitchen, garage, attic, or a loft. Anywhere there are fumes, dust, or a bit of smoke are good places to have a heat detector. These particles can get into a smoke detector and possibly cause it to malfunction and give many false-positives.