Relationship Between Smoke And Heat Detectors

You are welcome to this review on the relationship between smoke detectors and heat detectors. You should have a seat, with a drink in your hand, as you read through this guide, we’ll see the relationship between smoke and heat detectors. By the end of this review, if you have been having second thoughts on which detector to go for, you’ll be able to decide which you need.

A heat detector is not the same device as a fire alarm. In fact, the two devices are very different. A fire alarm, or smoke alarm, reacts to smoke, while the heat detector reacts to heat. They have the same purpose but have different reaction times and different mechanisms.

What Is A Smoke Detector

Smoke Detectors are designed to protect people and buildings during the early signs of fire. Some fires do not accumulate a flame until after it has been burning for a while. While there is no flame to indicate a fire there is smoke. Smoke or poisonous fumes are the leading cause of harm during a fire. This makes smoke detectors crucial for homes and occupied businesses.

There are two variations of smoke detectors: optical smoke detectors and ionization detectors.

  • Optical Smoke Detector

Optical smoke detectors sense smoke using an LED light. The light is shone within a small chamber inside the device. When smoke enters the chamber, the light is scattered, and the LED beam is broken (disrupted due to the smoke). When the beam is broken, the alarm is triggered.

  • Ionization Smoke Detector

An ionization detector uses an ionized chamber. To ionize the chamber, the device exposes a catalyst to the air. On one side of the chamber, there is a small hole for smoke to enter. When smoke enters the chamber, the ionization decreases, triggering the alarm. Even the smallest amount of smoke will cause the alarm to go off.

Smoke detectors sense fires within the first few moments. Smoke is the first sign of a fire, meaning that smoke detectors typically sense the fire quickly and efficiently. With a smoke sensor, fires are noticed and put out long before the fire can spread.

Smoke detectors are the most efficient way to detect a fire. Because there is typically smoke before a drastic heat change, smoke detectors sense fires faster than heat sensors. For everyday use in the home, smoke detectors are the best way to detect a fire.

However, smoke detectors can be triggered falsely by dust, meaning that they are not the best device for dusty spaces such as attics or basements. Since heat sensors won’t be triggered falsely due to dust, they are the best device for that job.

What Is A Heat Detector?

Heat Detectors are designed to sense temperature change caused by fire. Fire causes detrimental damage to buildings. Detecting fire heat is very important to make sure a fire does not get out of control. Heat detectors are mostly for buildings where the building is the main concern.

The main property of a heat sensor is to sense the heat, which is present around the sensor. When the set value of the temperature is high, then it is indicated with the help of a glowing LED. The usage of the heat sensor circuit is inside your PC or in your kitchen.

Due to overheating, the expensive components present in the PC or kitchen appliances could be damaged. When the temperature around the heat sensor increases above its set value, then it senses the heat and gives an indication, so that we can protect the devices from damage. The heat sensor circuit senses the heat from various electronic devices like amplifiers, computers, etc, and thus generates the warning alarm.

Based on the operation, the heat detectors are mainly classified into two types

  • Fixed Temperature Heat Detectors
  • The rate of rising Heat Detectors

Fixed Temperature Heat Detector

There are two heat-sensitive thermocouples in a heat detector. One thermocouple responds to ambient temperature. The other thermocouple is used to monitor the heat, which is transferred by radiation or convection. The heat detector operates irrespective of the starting temperature.

The temperature rises from 12˚ to 15˚F per minute. These detectors can be operated at low-temperature fire conditions if the type of heat detector threshold value is fixed.

A rate of rising Heat Detector

It doesn’t respond to low energy release rates that deliberately develop fires. These combination detectors add a fixed temperature element which is used for detecting slowly developing fires. This element responds whenever a fixed temperature element reaches the threshold. Generally, an electrically connected fixed temperature point is 136.4˚F or 58˚ C.

How does a heat detector work?

There are two types of heat detectors which, although they operate differently, essentially provide the same outcome.

Electro-pneumatic heat detectors contain a diaphragm that moves when there is a change in pressure owing to a shift in the ambient temperature. When the diaphragm moves, an electric circuit is completed, which activates the alarm.

Rate of Rise – or ROR – heat detectors operate using two heat-sensitive thermocouples. One of the thermocouples monitors the heat transferred by convection or radiation while the other measures the background temperature of the room. An alarm sounds when there’s a disparity between the two, suggesting that a fire is about to break out.

Heat detector locations

The key to using heat detectors is knowing where to use them. Your heat detector location is vital for the safeguarding of your building. Although it’s better to install a heat detector in the center of your room’s ceiling, you can position it on a wall, 50cm or so below the ceiling height.

Heat detectors are perfect to use where a smoke alarm isn’t suitable – for instance, in rooms where there are high levels of smoke, fumes, and dust, like garages or lofts. It’s also a good idea to use a heat detector in areas where chemicals or highly flammable substances are stored.

Heat detector circuit

Each heat detector covers an area of 5 meters squared but it is possible to link up to 20 heat detectors in any given circuit, providing a range of up to 100 meters. The benefit of this, of course, is that you can protect your whole building within one heat detector circuit. If a fire breaks out in the basement, you’ll be alerted by your nearest heat detector, even if you’re on the very top floor of the building.

Sentinel’s heat detectors are ideally suited for use in a circuit since they are completely wire-free, so can be installed with a minimum of fuss and mess.

Heat detector spacing

It’s important to think about the spacing of heat detectors ahead of time. Position your heat alarm as close to the center of the room as possible to ensure that the entire vicinity is covered. Also, choose a spot that is at least 10cm from a wall or corner.

The strengths of smoke detectors are:

  • Detects Fires Quickly. Smoke detectors are the fastest way to detect fires. Since smoke is produced as soon as the fire starts, the detector can alert the homeowner seconds after the fire starts.
  • Smart Capacity. Smoke detectors can be “smart,” meaning that they can be installed with a wireless home security system and synced with your mobile device. With this ability, the smoke detector can alert the homeowner to a house fire even when the homeowner is away. Rather than waiting for a neighbor to notice flames in the window, smoke detectors allow homeowners to proactively protect their homes and call for the fire department seconds after the fire has started.
  • Detects Low Energy Fires. Not all fires are the same. Some fires, called low energy fires, emit only a small amount of heat but lots of smoke. These fires are hard for other fire detectors to sense. A smoke detector, on the other hand, can detect low energy fires faster than any other device on the market.

The strengths of a heat detector are:

  • Less Prone to False Alarms. While smoke detectors are prone to false alarms, heat detectors are harder to fool. Heat detectors rely on the actual temperature of the room, and, if the temperature of the room hasn’t increased, the alarm won’t be activated.
  • Protects Attics and Basements. Smoke detectors struggle to protect attics and basements due to the dust and other particles in the air. Heat sensors, on the other hand, can easily protect their areas without losing their efficiency. They maintain their effectiveness in a variety of rooms and situations.
  • Used With Ceiling Sprinklers. Heat detectors are the number one choice for triggering ceiling sprinklers in a building. The last thing that a business would want is a false alarm that activates the sprinklers. However, if there is a fire, ceiling sprinklers can save the building. Because heat detectors are incredibly effective and hard to fool, they are the best choice for this job.

In a nutshell, here’s the difference between heat detectors and smoke detectors:

Heat detectors are intended to minimize property damage by reacting to the change in temperature caused by a fire

Smoke detectors are intended to protect people and property by generating an alarm earlier in the development of a fire. People need time to react, and every second is critical during an actual fire event.

When it comes to protecting people, it is critical to warn building occupants before smoke accumulates. Some types of fires “smolder,” or burn very slowly without flames. Burning slowly causes incomplete combustion, which in turn generates more smoke, carbon monoxide, and other poisonous gases. Smoldering fires also generate very little heat, making them difficult to detect with heat detectors. When people are harmed during a fire, the culprit is almost always smoke and poisonous gases like CO: not the heat or flames.


If you have a strict budget it is possible to provide more than adequate fire protection in your home or fire alarm system by positioning the best detector for the job in certain areas. However, for the best possible fire detection, a combination of devices in all areas (except those where nuisance alarms may be caused e.g. kitchens) will provide the optimal level of cover and ensure that fire alarms are activated without delay in the event of a fire.

It should also be noted that smoke detectors and heat detectors do not provide the same area of coverage.