Testing Smoke and Carbon Monoxide Detectors

Smoke and Carbon Monoxide detectors are among the most important home safety systems. They give early warning signs that alert your family of dangerous smoke and rising Carbon Monoxide levels.

These devices give you time to evacuate the building before the situation gets worse, and may even call the fire department. As a result, you are guaranteed safety and prompt response services.

However, smoke and Carbon Monoxide detectors need periodic testing and battery replacement. So, let’s learn How to Test Your Smoke and Carbon Monoxide Detectors to guarantee optimal operation.

The first step in testing your smoke and Carbon Monoxide detectors involves warning the building’s occupants of the operation. Otherwise, the noise may startle them and cause unnecessary panic.

Then, perform a sound test by holding the ‘test’ button for some seconds until you hear the alarm. Replace the device if the alarm does not sound yet it has functional batteries.

Finally, test the detectors with canned smoke. Hold the tester two to three feet from the device and spray for thirty seconds. If the alarm does not sound within five seconds, assess it for a malfunction.

That said, read this article till the end for more understanding on how smoke and carbon monoxide detectors work. It will also shed more light on how to conduct functionality tests without needing a professional.

What Is Smoke Detector?

Testing Your Smoke and Carbon Monoxide Detectors
A Smoke Detector

A smoke detector is a gadget that detects smoke particles as a primary fire indicator. It gives a signal for fire alarm systems in large buildings. The unit also produces a visual and audible signal in a home or room.

Smoke detectors are found in tiny, round shaped plastic cases and positioned in strategic areas in a facility. They detect smoke particles in the air using two technologies: photoelectric and ionization.

Photoelectric technology works by detecting reflected light particles from a light beam in the sensing chamber. The light from the beam doesn’t strike the detector in the absence of particles, indicating all clear. 

However, when there are particles in the air, the light registered by the detector exceeds the stipulated threshold level and triggers the alarm.

On the other hand, ionization technology uses bits of safely shielded radioactive material, which electrically charges and ionizes the air particles between two metal plates. As a result, electric current flows from one plate to the other.

When particles enter the device, they attract ions, carrying them away, and reducing the electric current. Further, when these particles are enough to reduce the current below a specified level, the detector registers them as smoke and triggers the alarm.

Based on the above technologies, smoke detectors come into types: Photoelectric and ionization smoke detectors. Below is how they work and what to expect from them.

  1. Photoelectric Smoke Detectors

These smoke detectors use photoelectric technology with the main component being a light beam chamber. Further, the chamber has a light beam emitter and a light receptor. As long as the light continuously strikes the detector or receptor, the alarm remains off.

However, smoke and soot in the device hinder the light beam from hitting the detector. As such, the unit produces an alarm.

Photoelectric smoke detectors are perfect for detecting smoldering fires that give off large smoke and soot particles.

  1. Ionization Smoke Detector

These smoke detectors have internal components housing an ionization section with two plates. The plates have a radioactive and shielded material that continuously generates electric current.

The ionization section produces a small electricity current flowing from one plate to the other. Hence, the air between the two plates is always electrically ionized or charged.

Foreign particles in the smoke detector interfere with the airspace between the two chambers. They attract the ions between the metal plates, disrupting the electricity flow. And the more the molecules the less the current, which activates the alarm.

Ionization smoke detectors are suitable for detecting fires flaming hot with tiny smoke particles or black soot and hot gasses.

Thankfully, having either photoelectric or ionization smoke detectors in your business or home makes no difference. They are very smoke sensitive and reliable in identifying smoke caused by fire combustion and burning.

However, although both smoke detectors can detect either fast burning and flaming fires or slow-burning and smoldering fires, each technology features unique strengths. 

For instance, photoelectric-based devices are more sensitive to large and light-colored particles, whereas ionization-based ones are better for small black soot molecules from flaming fires.

So, it is prudent to consider the third type of smoke detectors that maximizes both technologies.

  1. Dual Sensor Smoke Detectors

The National Fire Protection Association (NFPA) advises home and business owners to get dual sensor devices. So, they do not have to install both photoelectric and ionization detectors in one facility.

By using photoelectric and ionization technology, dual sensor smoke detectors guarantee the earliest possible alert, regardless of the type of fire.

As important as smoke detectors are for keeping your family and property safe, sometimes they are a nuisance. For example, devices near the kitchen detect smoke particles from cooking food. Moreover, something as harmless as turning on a toaster can activate the alarm.

Therefore, as with most safety measures, these units have a trade-off. You can make them sensitive enough to sense any smoke. But this leads them to detect smoke from safe sources and even dust.

On the other hand, less sensitive smoke detectors have fewer false alarms. But they may not give a signal or go off in time during an actual fire. As such, the system fails to do its job: save lives.

Fortunately, the next generation of detectors promises to reduce nuisance alarms and enhance the unit’s ability to signal real fires quickly. Remember, time is everything in a fire hazard.

What Is Carbon Monoxide Detector? 

Testing Your Smoke and Carbon Monoxide Detectors
Carbon Monoxide Detector

Carbon Monoxide successfully flies under the radar of human detection. Therefore, it easily spreads in an area, causing CO poisoning to occupants. And thus, we need a technology to identify the gas immediately so that prompt action is taken.

Thankfully, Carbon Monoxide detectors utilize how the gas alters the electric resistance or color of various materials. Sometimes, it also fosters atmospheric electrochemical reactions, which helps measure how much of the gas is around.

You cannot smell, taste, or see Carbon Monoxide, yet in abundance it kills within minutes. Besides, the gas is called the invisible or silent killer when it seeps from misused or broken heating units at hazardous levels.

Vehicles, portable indoor operated generators, and faulty furnaces or stoves are potential culprits of CO poisoning. These accidents kill hundreds of thousands and hospitalize tens of thousands annually in the United States.

That is why we have Carbon Monoxide detectors to alert us before danger looms. The devices measure the CO gas concentration in the air in parts per million (PPM). Then, they trigger the alarm if the gas exceeds certain levels.

Carbon Monoxide at 70 PPM triggers the alarm if detected in a few hours. On the other end of the metric, dangerous levels above 400 PPM activate the system within a few minutes.

In any case, the smoke detectors should give enough notice to allow people to escape before symptoms like headache, nausea, and unconsciousness take hold. Also, we should have safety standards to ensure that the alarms sound at the right time.

Various Carbon Monoxide detectors use different technologies to identify CO gas. For example, some devices have electrochemical sensors composed of electrodes submerged in an electrolyte.

Carbon Monoxide triggers a chemical reaction in the gas-permeable compartment housing the sensor. Further, the electrical current in the electrolyte surges and registers high CO concentration.

Other Carbon Monoxide detectors use metal sensors and depend on circuitry, instead of a chemical solution. When CO meets a sensor’s chip, it lowers its resistance to electricity flow, depending on the CO’s concentration.

A different approach imitates hemoglobin, a protein in body cells that facilitates oxygen flow to your tissues. However, it is easily hijacked by high CO levels. When Carbon Monoxide or Oxygen is chemically attached to hemoglobin, its color brightens and shifts the blood hue to cherry red.

So, Carbon Monoxide detectors mimicking the above technology have gel that changes color with high Carbon Monoxide levels. In addition, a light sensor tracks this color change to indicate CO concentration.

Although we have multiple technologies to select, any operational Carbon Monoxide detector significantly cuts down the risk of CO poisoning. Moreover, the National Fire Protection Association recommends mounting the devices per the manufacturer’s instructions.

Position Carbon Monoxide detectors in central locations outside bedrooms and every floor of the house. Also, check out local codes, laws, and standards for additional safety requirements.

All CO detectors have a limited lifetime. But the exact duration varies between brands and manufacturers. Hence, consult with the product’s expiration date and replace expired units.

We have various types of Carbon Monoxide detectors. They include

  1. Hardwired Carbon Monoxide Detectors

These units are directly connected to your business or home’s power supply and have a battery-backup. Thus, they will not malfunction or go off due to power related issues and outages.

Since the hardwired units must be directly connected to the power supply, consider getting professional installation. Otherwise, unless you are a licensed installer or qualified electrician you may not deliver a successful project.

  1. Digital Read-Out Detectors

These gadgets are recommended from home use and feature a display panel. Here, you can see the current and previous Carbon Monoxide concentration in parts per million. It also helps determine whether the detector is operating optimally, allowing you to activate the alarm when need be.

For example, if you notice lower Carbon Monoxide levels that normally trigger the system are being maintained over a long duration, you immediately know there is something wrong with the unit. Thus, you can take action before the issue gets out of hand.

  1. AC Plug-in

These Carbon Monoxide detectors are plugged into electricity outlets in a facility. This feature provides added convenience as you do not need to remember when to replace the batteries. However, most AC-plug in devices have back-up batteries for power outages.

Home safety experts recommend this CO detector for homes since it should be positioned at eye level on a wall. But remember, some power outlets are closer to the floor. So, get a long AC cable for the installation.

  1. Interconnected

These CO sensors connect wirelessly or using cables with other monitors and alarms, including burglar, smoke, and Carbon Monoxide alarms. Further, they relay emergency alarms from other parts of the facility.

As a result, consider interconnected Carbon Monoxide detectors in commercial buildings, such as offices.

  1. Combined Smoke and Carbon Monoxide Detectors

As the name suggests, these detectors feature smoke and Carbon Monoxide sensors. They sound the alarm after detecting either smoke or CO particles in the atmosphere.

However, we do not recommend these detectors because each detector type has a different positioning. Smoke detectors are best set on the ceiling, whereas Carbon Monoxide detectors work better on the wall.

  1. Portable/Handheld Carbon Monoxide Detectors

These gadgets are not ideal for home environments. Instead, their primary application is in government or commercial safety inspection roles.

How to Test Carbon Monoxide Detector

Installing a Carbon Monoxide detector on your property helps protect occupants from CO poisoning. However, you are only sure of maximum safety if the device works properly. Therefore, check the detector regularly with a special tester spray and check the alarm circuitry monthly by pressing the text button.

Below are various ways to test your Carbon Monoxide detector.

  1. Method One. Test the CO Sensor with Canned CO Test Gas
  • Purchase Carbon Monoxide detector tester spray from any home improvement store or online. One costs between $8 to $15 and lasts for a few years. Also, ensure the tester is a non-flammable aerosol.
  • Inhaling canned Carbon Monoxide or interacting with the spay is not dangerous. The gas is at a low concentration and is not harmful unless it is illegally concentrated.
  • Follow the manufacturer’s directive for the proper use of the test spray. Further, use a plastic bag to enclose the Carbon Monoxide detector and the spray nozzle tightly. Then, spray the canned CO test spray for three seconds.
  • You need to spray enough Carbon Monoxide so that your CO detector can pick up the gas in the canned test spray. Hold the sprayer for three seconds and observe. A working Carbon Monoxide detector sounds the alarm in fifteen minutes at 500 PPM.
  • You can get a testing device that holds the spray and seals around the detector while you test the unit. If the alarm does not go off, replace the batteries or the unit.
  • Remove the sprayer and test bag from the Carbon Monoxide detector and fan the latter with fresh air. Push the hush or test button near the LED light to turn off the alarm. This is also the battery test button that sounds the alarm when you’re testing the battery. 
  • Repeat the CO spray test annually to confirm whether your Carbon Monoxide detector is working. Also, check the test button monthly and change the unit’s batteries semi-annually. 
  1. Method Two: Test the Alarm’s Circuitry
  • Find the test button on your Carbon Monoxide detector. Its exact location and appearance varies from unit to unit. But you’ll mostly find it next to an LED light that’s periodically flashing.
  • Press the test button to sound the alarm for three to five seconds, that is, if the circuitry in your detector is functional. The alarm will be quite loud, cover or plug your ears.
  • Change the CO detector’s batteries in case the alarm does not sound. Further, if it does not sound after changing the batteries, replace the entire unit.
  • Some CO detectors have a sealed ten-year battery and a default timer to alert you when they need replacement. They beep and chirp periodically, informing you they need replacement.
  • Repeat the push-button test monthly. Have a set day per month, say every first day of the new month to test your Carbon Monoxide detector. This way, you will remember to do it.

Here’s How to Test Carbon Monoxide Detector:

How to Test Smoke Detector

Averagely, ten people die daily in the United States because of house fires. Good thing, the widespread use of smoke detectors has significantly decreased house related fire injuries and deaths.

However, smoke detectors are only useful if they function properly. Otherwise, a failing unit can let you down when you need it the most.

Below is a simple way to test whether your smoke detectors are working.

  1. Warn Family Members

Alert everyone in the home that you’ll be testing the smoke detector. This way, they won’t be surprised when the unit goes off. Also, notify the security unit’s company that you’re performing a test lest the fire department shows up at your door.

  1. Ask for Help

The alarm will sound very loud because you’ll be standing beneath it. However, you want it to be loud enough for anyone in the house. Therefore, have someone else stand farthest away from the smoke detector during the test.

  1. Test the Power

Most smoke detectors have a light that indicates whether the system is receiving power. But still, use the test button to guarantee that the alarm will sound.

Pressing the button sounds the alarm. If not, replace the unit’s batteries or get an electrician to check the wiring for a hardwired detector.

You can stand on a ladder or chair to reach the smoke detector. Alternatively, use a broom handle to press the button.

Some detectors go off on their own after a few seconds. But others need you to press the test button again. Also, you’ll get units that go into ‘programming mode’ if you hold the button for more than one second.

  1. Test the Smoke Detector Using an Aerosol Spray

Get an affordable aerosol spray specifically designed for testing smoke detectors. If the test does not sound the alarm, confirm whether you’re using the product as instructed by the manufacturer or if it is worn out.

Switch off the alarm after testing using a small hand-held vacuum. It sucks away the test material from the smoke sensor. Some devices also have a ‘silence’ button to stop the alarm.

  1. Test the Sensor With Real Smoke

Light two or three matches. Then, hold them a few feet underneath the smoke detector. The smoke causes the alarm to sound and confirms whether it is functioning properly. If it does not sound, replace the unit immediately.

However, keep the matches a few feet from the devices lest you melt or damage it. In addition, professionals do not recommend this test as it temporarily reduces the smoke detector’s effectiveness.

  1. Test the Smoke Detector Monthly

Plan a monthly schedule to check every smoke detector. Also, you can test it weekly if you can. This way, you are likely to identify a malfunctioning unit quickly.

In addition, you only need 30 minutes to an hour monthly to check all the detectors in the facility. This is more efficient than verifying each detector at different intervals.

How to Test Smoke Alarm:

Should My Carbon Monoxide Detector Have a Green Light?

A flashing green light simply means that the device is working. It also flashes when you press the test button to confirm optimal functionality. Therefore, you should not stop the CO detector’s green light.

A green light on a detector means that it is time to replace the battery, especially when it is also beeping. Thus, always check the Carbon Monoxide detector’s manual to interpret its signals.

What Are Two Warning Signs of Carbon Monoxide Poisoning?

Inhaling Carbon Monoxide poses a danger to your health with prolonged exposure. Hence, it is safe to know the signs of CO poisoning to avoid confusing the condition with another type of illness.

The primary warning signs of Carbon Monoxide poisoning include

  • Feeling Dizzy and Weak

Dizziness is among the early warning signs of CO poisoning. The gas affects oxygen levels in your blood causing you to feel dizzy. In addition, you’ll feel weak and tired, unable to move around enthusiastically.

  • Severe Headache

A headache is also an early sign of CO poisoning. It does not take long to have headaches if there is a Carbon Monoxide leak. Therefore, evacuate the home or building immediately and seek medical assistance.

What’s the Difference Between Fire Detector and Smoke Detector?

Fire and smoke detectors are among the most essential items in a home. However, most homeowners do not know the difference between a fire detector and a smoke detector. As such, they don’t know whether to install either device or both.

Let’s examine each device for better understanding and differentiation.

  • Fire Detectors

A fire detector is a unit that senses the presence of fire. It comprises smoke and combustible gas detectors that detect fire hazards. Usually, smoke detectors use electrochemical and optical sensors, whereas combustible gas detectors use catalytic or electrochemical cell sensors.

Fire detectors alert emergency responses from the fire department and simultaneously trigger other security systems. These latter units include lighting management systems, access controls, sprinklers, and ambient sound systems.

The devices also have sirens and a set of lights to alert hearing impaired family members. This way, everybody in the building can tell there is an emergency.

Remember, fire detectors do not play the leading role in fighting against fire. Instead, they prevent it and it’s spread and warn you early enough to prevent fire related injuries and deaths.

  • Smoke Detectors

A smoke detector is a fire fighting gadget that alerts you after sensing intense smoke levels. It also gives an audible alarm notifying all in the vicinity to evacuate. In addition, you can configure the system to alert the fire department anytime it goes off.

These devices have sensors with a certain sensitivity level that identifies hazardous fumes dues to their density and composition. They also come in various modern technologies to show the level of dirt and smoke particles.

Smoke detectors produce an acoustic signal to warn a building’s occupants of smoke and vapor molecules in the air that can generate a fire. Further, they are battery-powered to avoid malfunctions related to power supply issues.

Personnel from a central monitoring station can check the concentration of dirt and smoke particles in the air through a software application. Also, schedule a technical check to avoid false alarms due to poor maintenance.

There are multiple ways to sense smoke traces in the atmosphere. The most used technology in smoke detectors is optical detection. The units have a photoelectric cell that evaluates how light beams behave. 

Any interruption to transmitted light registers as a smoke hazard. Therefore, the detector gives an alarm to warn that a fire is occurring. Further, the unit can monitor spaces of  30m² with a height of 6m.

That said, please note that smoke detectors are only sensors and detect smoke but fire detectors detect fire and alert the control system. Also, you can connect fire detectors with multiple devices, including a smoke detector to guarantee maximum protection.


Smoke and Carbon Monoxide detectors are important devices to an all-encompassing home security unit. They are life-saving gadgets, but you must confirm they are working properly for guaranteed safety.

Thankfully, testing these detectors is rather straightforward and needs minimum tools. Moreover, with practice and setting reminders, you can ensure the safety unit operates optimally at all times.

The above write-up gives you a simple procedure to follow when testing your smoke and CO detectors. It breaks down what each device is, signals to watch out for, and how to test the unit for the best result.

Testing Smoke and Carbon Monoxide Detectors

Press the test button on your smoke or Carbon Monoxide detector for about three seconds. Normally, you should hear a siren or an alarm after one or two seconds. Otherwise, the system has low batteries or is malfunctioning.

Also, have someone walk to other rooms to confirm that the alarm is heard throughout. If the siren is too low, replace the battery or the entire unit.

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