Do Fire Alarms Detect Gas?


During a fire accident, the most critical aspect in surviving is getting out quickly, which is why it’s so important to have a working fire alarm system.

While a fire alarm system contains many devices working together to detect smoke and fire, the question is, do fire alarms also detect gas? Fire alarms can consist of various types of detectors, but these detectors (except carbon monoxide detectors) are not able to detect gas. They only detect the smoke and then initiate the alarm. A carbon monoxide detector, also known as a CO detector, only detects carbon monoxide gas and not natural gas as the nature of both gases is different. 

A fire alarm system consists of various types of detectors that need to be discussed in detail to understand them properly. Moreover, it is also essential to know about the benefits of having a carbon monoxide detector at home.


What is a Fire Alarm System?

Fire alarm systems are installed to alert us about emergencies to take timely actions to protect ourselves. Fire alarms are installed in homes, offices, schools, and public buildings and perform a significant role at the time of fire emergencies.

A fire alarm activates when a detector detects an issue in the building or home and notifies the residents to evict the building. 

In a fire alarm system or fire detector system, the control panel acts as a brain as it is the central hub for all the detectors to be wired.


Types of Fire Alarm Detectors

There is a wide array of detecting devices, from the efficient smoke detector to manual break glass units, that are divided into groups like:

  • Heat detectors
  • Smoke detectors
  • Multi-sensor detectors
  • Manual Call Points
  • Carbon Monoxide detectors


Heat Detectors

A heat detector works in two ways. The first one is that detectors work on a temperature that’s set by the resident, and if the temperature exceeds the given limit, it will activate the alarm. The second method is that the detector works on the rate of temperature change.

A heat detector performs its function in a similar way to an electrical fuse. The heat detector consists of a heat-sensitive eutectic alloy that transforms from solid into liquid at a certain temperature and triggers the fire alarm.


Smoke Detectors

Smoke detectors are of three main types including:

  • Ionized Smoke Detectors
  • Light Scattering Smoke Detectors
  • Light Obscuring Smoke Detectors


  • Ionized Smoke Detectors

There are generally two chambers in an ionized smoke detector; one chamber is used to compensate for the temperature, humidity, or pressure change.

While the other chamber has a radioactive source (alpha particle) that ionizes the air, it passes through the chamber, where the current flows between two electrodes.

When there is smoke in the room, it will enter the ionized detector and decrease current flow. This decrease in current flow becomes a source of initiating an alarm.


  • Light Scattering Smoke Detectors

In light scattering smoke detectors, the light source and photocell are separated by a darkened chamber. This darkened cell is used for the light source to fall on the photocell. 

When the smoke enters the chamber, the light scatters and falls on the photocell that initiates the alarm.


  • Light Obscuring Smoke Detectors

Smoke interferes between the light source and a photocell in the light obscuring smoke detector, and the photocell measures the amount of light received.

The variation due to smoke in the output of the photocell is used to initiate the alarm. This type of smoke detector is generally used in larger areas where a light source or a photocell is placed at some distance.


Multi-sensor Detectors

Multi-sensor detectors use optical and heat sensors and combine their inputs to detect the fire. Their input is processed by an algorithm that is built in the detector circuitry. 

When the inputs from both sensors are transferred to the control panel, the control panel then returns a value based on both inputs. Such detectors are designed for a wide range of fires.


Manual Call Points

A manual call point, known as a break glass call point, allows you to raise the alarm by breaking the glass or plastic. Such manual call points are preferably installed at high-risk areas like cookers, kitchens, exits, corridors, and fire escapes.


Carbon Monoxide Detectors

Carbon dioxide is a poisonous gas that can cause breathing problems and, at a high level, can be a life threat. Carbon Monoxide detectors, also known as CO fire detectors, are electronic detectors used by the residents to detect carbon monoxide in the house. These detectors indicate the fire accident by sensing the level of carbon monoxide level in the air.

These detectors have an electrochemical cell that only detects the carbon monoxide gas and not smoke or any other combustion product.

Related posts you may wish to read related to carbon monoxide detectors:


Benefits of Carbon Monoxide Alarms

Carbon monoxide gas is a dangerous gas that is produced due to an incomplete burn of a by-product. Carbon monoxide can enter the house through various sources like the faulty furnace, gas-powered fireplace, or a cloth dryer.

This gas is dangerous as it is odorless, colorless, but highly flammable. It can slowly accumulate in a home over a long term, an this can be just as dangerous a threat to your life as a sudden spike in carbon monoxide. Many people die in their sleep due to carbon monoxide suffocation as carbon monoxide blocks the air passage in your lungs when you inhale it.

Those who get poisoned by this gas feel dizzy. They may try to take a nap due to dizziness instead of checking for a gas leak. Therefore, the homeowners should be well aware of the risks associated with carbon monoxide and take preventive measures by regular maintenance and inspection.


Symptoms of Carbon Monoxide Poisoning

Symptoms of carbon monoxide can be simple, like the symptoms of flu with less fever. These symptoms include:

  • Vomiting
  • Dizziness
  • Blurry vision
  • Weakness
  • Disorientation
  • Passing out
  • Rapid heartbeat
  • Respiratory failure
  • Seizures

If you feel these symptoms at home and feel better when you go outside can be another indication.


Types of Carbon Monoxide Detectors

A carbon monoxide detector is used as it senses the carbon monoxide level in a room and warns about the presence of fire. These detectors are purely carbon monoxide detectors and only respond to CO and not to the smoke.

A type of CO detector is a Patch or Blob detector that changes the color when carbon monoxide touches it. The presence of carbon monoxide oxidizes the strip that notifies the resident about the risk of carbon monoxide.

An advantage of this type of detector is that it is cheap, but a disadvantage is that the user will have to keep an eye on it because it is not an audible alarm. Moreover, the strips or blob need replacing after every few months.

The most common type of detector is electronic CO that is a little costly than the blob detector, but it is audible and can alert the resident about the increase in the level of carbon monoxide.

Another form of carbon monoxide detector is a sealed detector, which the users can’t tamper with. Their batteries last up to 10 years. When the battery is about to die, it is notified by an alarm.

Such detectors are usually used in rented houses so that the tenants can’t remove them or take the batteries out.

Lastly, be careful which carbon monoxide detector you choose. This is one thing in your home you don’t want to be cheap about.

Because carbon monoxide is odorless and colorless, it’s virtually impossible to sense until it’s too late. Don’t make the mistake of buying one that’s questionable and cheap. The EPA recommends getting a carbon monoxide detector that either follows Underwriters Laboratory (UL) standard 2034 or the International Approval Services (IAS) 6-96 standard.


Related Questions

Does a carbon monoxide detector detect gas?

A carbon monoxide detector only detects carbon monoxide produced by fire and is not able to detect natural gas as it is an entirely different gas. Moreover, most fire detectors only detect carbon monoxide because it is considered a threat to life. 

Natural gas is more volatile and easily detectable without detectors, but a homeowner can purchase a detector that can detect different types of gas leaks to increase safety and security.


Where should the carbon monoxide detector be placed?

You can place the carbon monoxide alarm in these three most critical places of your home so that everyone can hear it.

  • On every level, including basement and attic
  • Near or in bedrooms and sleeping spaces
  • By the door that leads to the attached garage

For additional guidance, you can check the manufacturer’s instruction and local laws to see any other location other than the three mentioned because, in some places, a sensor in the utility room is required.


Why is my electric fire alarm beeping?

This typically happens when the battery is low, in which case you’ll obviously need to replace it. But if the alarm still has the green light on and has a working main battery or backup battery, it may just be that you need to press the reset button instead. Check your manufacturer’s instructions.


Should you have a smoke detector in every room?

This will depend on the laws of your state and local jurisdiction, but typically, smoke alarms are either placed in each bedroom individually or in a nearby common area that each bedroom has access to (such as a shared hallway).

Other common practices are to have at least one fire alarm on each level of the home, as well as more dangerous areas of the home like in the garage, kitchen, laundry room, or near a heater or fireplace.


Is a fire alarm the same as a smoke detector?

No, a smoke detector merely picks up the presence of smoke and makes a sound just in the specific area of the home where it’s activated. A fire alarm, on the other hand, goes further by acting on the trigger. It may activate sprinkler systems, alert the local fire department, and perform other actions across the entire home. A fire alarm system may utilize smoke detectors as part of it, but it’s just one component of what makes a comprehensive fire alarm system.