All About Smoke Detectors and Carbon Monoxide Detectors

The importance of these life-saving devices.

Fires or high levels of carbon monoxide in the workplace can be devastating. They can threaten the lives of your employees and wreak havoc on your facility. Besides a sound emergency preparedness plan, smoke and carbon monoxide detectors are your first line of defense in a fire or gas-leak emergency. 

Before you purchase your smoke alarms or carbon monoxide detection systems, always check in with your local building department to ensure you purchase the right ones for your workplace.


Why Fire and Carbon Monoxide Detection Is So Important 

Automatic fire detection systems are designed to quickly detect a fire and immediately alert onsite employees to vacate the premises. These systems can also alert emergency response personnel to respond to the fire to reduce injury, loss of life, and structural damage. Automatic fire detection systems detect smoke, heat, flames, or fire via electronic sensors.

If you have equipped your workplace with a fire detection system that complies with OSHA’s standards, keep in mind that your system must also comply with the "Fire Detection Systems" standard. [29 CFR 1910.164]

Carbon monoxide is a poisonous, odorless, colorless, tasteless gas. When breathed in, the gas displaces oxygen in the bloodstream and can cause irreversible harm to vital organs. If CO is at high levels, loss of consciousness or suffocation can happen in just minutes. 

To help prevent these worst-case scenarios, let’s explore the different types of smoke and CO alarms to determine which ones are right for your business.


What Is a Smoke Detector?

Whether you’re in an office building, warehouse, manufacturing facility, retail environment, restaurant, school, hotel, or another type of building, you know how important smoke detectors are in case the unthinkable occurs. 

But what exactly is a smoke detector? Quite simply, they are devices that electronically sense smoke and will sound an alarm, initiate strobe lights, or make voice commands (or all three) to warn occupants that a fire is present in the building. In commercial buildings, smoke detectors may alert a fire alarm control panel (FACP) that will set off a set of functions, depending on the type of fire panel the building has. There are three main types of smoke detectors.

Photoelectric Smoke Detectors

Photoelectric smoke detectors utilize a light beam to detect smoke. When the chunky particles of the smoke enter the chamber, the light beam is disrupted and scattered, thereby triggering the alarm. Photoelectric sensors are best for detecting slow-burning, smoldering fires that produce harmful smoke and gas. 

Ionization Smoke Detectors

Ionization smoke detectors are made with a small amount of radioactive material placed between two electrodes that ionize the air. When smoke enters the chamber, the ions are disrupted and the alarm sounds. Ionization smoke detectors are best for detecting fast-burning, flaming fires.

Dual-Sensor Smoke Detectors

You can also equip your facility with dual-sensor smoke detectors that harness the technology of photoelectric and ionization detectors. That way, your building will be prepared for both smoky, slow-burning fires and fast-moving, flaming fires.


What Is a Carbon Monoxide Detector?

As mentioned earlier, carbon monoxide is a deadly odorless, colorless, tasteless gas that can cause irreparable bodily harm in just moments. Many occupations and industries pose a threat of accidental exposure to high levels of CO. Some of these professions include welders, firefighters, automotive mechanics, diesel engine operators, and those that work in boiler rooms, warehouses, steel production, and more.

Carbon Monoxide Detector

It’s imperative to equip your facility with CO detectors to protect your employees from exposure to carbon monoxide. If you’re wondering how a carbon monoxide detector works, they operate on a concentration-time function. For example, for lower amounts of carbon monoxide, such as 100ppm concentration, the alarm will not sound for up to an hour, while at 400ppm the alarm will sound within just a few minutes. . 

Dual Smoke and Carbon Monoxide Detectors

Dual smoke and carbon monoxide detectors help to reduce the number of alarms you may have in your facility. However, since some carbon monoxide detectors are installed low to the floor in outlets, the smoke alarm may be compromised because smoke alarms should be placed closer to the ceiling. In addition, most dual detectors have a carbon monoxide sensor and either an ionization smoke detector or photoelectric smoke detector, but rarely both. That means you may not be getting comprehensive protection from fires.


Use this chart to compare fire and carbon monoxide sensors.

Photoelectric Smoke Detectors Ionization Smoke Detectors Dual-Sensor Smoke Detectors Dual Smoke and Carbon Monoxide Detectors Carbon Monoxide Detectors

Utilizes a photo beam across the chamber. When smoke particles enter the chamber, the light beam is disrupted and the alarm sounds.

Utilizes radioactive material and electrons to ionize the air in a chamber. When the ions are disrupted, the alarm sounds.

Combines both photoelectric and ionization technologies to reduce the need for two types of smoke alarms.

Combines carbon monoxide and smoke detection in one device, reducing the number of alarms in your home or workplace. Utilizes sensors to detect the deadly, odorless, colorless gas when levels become too high.
Best for detecting smoldering, smoky fires. Best for detecting fast-moving, flaming fires. Comprehensive alarm for both smoky and fast, flaming fires. Most sensors have either photoelectric or ionization smoke detection technology, but seldom both.  Does not detect other gasses such as methane, natural gas, or propane.


Guidelines on Smoke and Carbon Monoxide Alarm Placement

Now that you have a sense of which types of smoke alarms and carbon monoxide sensors may be right for your business, it’s time to think about where you should place them. 

Where to Place Your Smoke Detectors

OSHA has laid out where to place your smoke alarms in your facility. Remember to always follow the manufacturer’s instructions as well. Refer to this excerpt from an OSHA webpage when designing your fire alarm system.

General Guidelines for Placing Fire Detectors

  • Place at least one detector in each room, storage area, and hallway. You may need more than one detector per room for those that exceed the manufacturer's spacing requirements. For example, if your detector is rated for 30 feet, install detectors so they are evenly spaced with no more than 30 feet between detectors.
  • Place the detector as close to the center of the ceiling as possible when only one detector is required in a room or space.
  • Place at least one detector in each closet, elevator, dumbwaiter shaft, stairwell, and other enclosed spaces.
  • Place a detector at the top of each flight of stairs.
  • Place the detectors in the path of the airflow toward the return air duct when air supply or return ducts are present in a room or space.
  • Place all smoke detectors at least 3 feet from ceiling fans.¹

Keep in mind that smoke detectors should be replaced every 10 years. You should replace the batteries twice a year unless your alarm has a lithium battery which can last up to 10 years. Make sure your alarms are in good working order every month. When you purchase your smoke detectors, look for the UL label to ensure they meet the Underwriters Laboratories standard.

Where to Place Your Carbon Monoxide Detectors

According to the U.S. Environmental Protection Agency (EPA), the ideal placement of carbon monoxide detectors is on a wall about 5 feet from the floor. This is because carbon monoxide is slightly lighter than air. You can also place CO detectors on the ceiling as CO is often found in warm, rising air. Don’t place a carbon monoxide sensor near a fireplace or fire-producing machinery or appliances, as you may get false detection of a high concentration of CO in the air. 

Carbon monoxide sensors should be replaced every 5-7 years. The EPA recommends that you test your detectors weekly and replace the battery every year. If your CO alarm starts chirping or beeping, the battery may be running out or there may be another mechanical malfunction that needs to be addressed. 

Always follow the manufacturer's instructions on spacing and placement when you install your CO detectors. Some general guidelines include making sure there’s at least 1 CO detector on every level of your facility, including the basement if you have one. Don’t place a CO detector near a door or window where fresh air is coming in because you may get a false low reading. When you purchase your CO detectors, look for the UL label to ensure they meet the Underwriters Laboratories standard.

Here is an excerpt on OSHA’s standards of CO exposure from its guide, OSHA Factsheet: Carbon Monoxide Poisoning. Keep in mind, PEL stands for permissible exposure limit.

  • The OSHA PEL for CO is 50 parts per million (ppm). OSHA standards prohibit worker exposure to more than 50 parts of CO gas per million parts of air averaged during an 8-hour time period. 
  • The 8-hour PEL for CO in maritime operations is also 50 ppm. Maritime workers, however, must be removed from exposure if the CO concentration in the atmosphere exceeds 100 ppm. The peak CO level for employees engaged in Ro-Ro operations (roll-on roll-off operations during cargo loading and unloading) is 200 ppm.²


Commercial Buildings

Industrial Buildings


Power Sources

Smoke Detectors 

Smoke detectors are either battery operated, hardwired to your facility’s electrical system, or can connect to an FACP. As mentioned before, battery-operated smoke alarms need regular testing and need their batteries changed twice a year.

Hardwired smoke alarms run on line voltage and have a battery backup in case the electricity shuts down due to the fire. Hardwired smoke alarms can sound smoke alarms throughout the building even if a fire isn’t present in a particular area. This can alert occupants to evacuate and get to safety as soon as possible. 

FACPs are required in many types of buildings and can orchestrate a variety of life- and property-saving responses including sounding building-wide alarms, turning on sprinkler systems, alerting the fire department, locking/unlocking doors, shutting down elevators, and more. For example, if a smoke alarm in a building senses smoke, it can send a signal to the FACP and the panel will initiate the sequence of actions it’s programmed to perform.

Carbon Monoxide Detectors

Carbon monoxide detectors are either battery-powered, hard-wired to a central electrical system, or plugged into an electrical socket. Hard-wired carbon monoxide detectors are often the top choice because of their accuracy and, in some cases, ability to alert emergency call centers if CO levels become dangerous.

Equipping your facility with the right type of smoke and CO detectors can bring peace of mind and buy time in case of a real-life emergency. As a reminder, always check in with your local building department to determine the right safety devices for your workplace. In addition, make sure to have a sound evacuation plan, hold frequent drills, and train your employees on the symptoms of CO exposure. 





Product Compliance and Suitability

The product statements contained in this guide are intended for general informational purposes only. Such product statements do not constitute a product recommendation or representation as to the appropriateness, accuracy, completeness, correctness, or currentness of the information provided. Information provided in this guide does not replace the use by you of any manufacturer instructions, technical product manual, or other professional resource or adviser available to you. Always read, understand, and follow all manufacturer instructions.