Four Things to Know about Smoke and CO Alarm Certifications and Technologies to Help Save Lives
Do you know what to look for in a smoke or carbon monoxide (CO) alarm? Certifications for these important safety products can vary, and not all testing standards evaluate the same performance criteria. Knowing the different certifications can help you better assess the safety, reliability, and effectiveness of alarm products.
Below are four ways certification and testing standards help take the guesswork out of choosing a safe alarm.
1. Certification Marks Offer Confidence
One of the simplest ways to evaluate a smoke alarm, a CO alarm, a combo alarm, or a smart smoke and CO alarm is to look for a recognized certification mark.
Marks such as the Underwriters Laboratory (UL) Seal or Intertek's ETL Listed Mark indicate the product has been independently tested and verified to meet established safety and performance standards in the U.S. and Canada. They are third-party evaluations designed to confirm the product performs as expected under defined safety conditions.
In Canada, consumers should also look for recognized certification marks such as ULC, cUL, CSA, or cETL, which indicate products have been evaluated to applicable Canadian safety standards and requirements.
When you see these marks, you can feel confident that the product has been independently evaluated to recognized safety and performance standards before it reaches your home.
| U.S. UL Mark | U.S. ETL Mark | Canada UL Mark | Canada ETL Mark | CSA Mark |
 |
 |
 |
 |
 |
2. Different Standards Test Different Safety Risks
Different certifications focus on different types of risk, and that distinction matters.
Some certifications focus on electrical safety, meaning the device has been evaluated for risks like overheating, fire, or electrical failure. These standards help ensure the alarm itself is safe to use in your home.
Other alarm standards in the U.S. and Canada focus on detection accuracy and response timing. These standards test whether an alarm can detect CO at specific concentrations and respond appropriately.
- CO alarm standard: UL 2034 is a recognized CO alarm standard that defines required response times based on exposure levels. These standards are designed to ensure alarms provide reliable early warning before carbon monoxide exposure becomes life-threatening, while also helping reduce the likelihood of unnecessary alarms from low-level, non-dangerous conditions.
- Smoke alarm standard: UL 217 reflects the evolving nature of residential fires and advancements in detection technology, to ensure that smoke alarms can reliably detect smoldering and flaming fires while reducing nuisance alarms.
3. CO Standards Require Fast Warnings at Dangerous Levels
CO alarms are tested to respond to carbon monoxide at certain concentration levels, often measured in parts per million (ppm) and it indicates how much CO is present in a space, relative to air molecules.
The CO alarm standard UL 2034, developed with input from the U.S. Consumer Product Safety Commission (CPSC) and recognized in both Canada and the U.S., defines specific response thresholds that determine how quickly a CO alarm must activate at different gas concentration levels. According to UL 2034, 70 ppm of CO is the lowest concentration level that requires alarm activation, and the alarm must activate within 60-240 minutes.
Under UL 2034:
- If the alarm is exposed to 400 ppm of CO, activation is required between 4 and 15 minutes
- If the alarm is exposed to 150 ppm of CO, activation is required between 10 and 50 minutes.
- If the alarm is exposed to 70 ppm of CO, activation is required between 60 and 240 minutes.
4. Independent Testing Helps Build Trust
By evaluating products against established safety standards, third-party testing organizations help ensure alarms meet defined performance and safety requirements before they reach the market.
Reputable manufacturers support this process by investing in research, development, and ongoing testing to help ensure their alarms perform as intended in real-world conditions. This commitment to safety and reliability is reflected in long-standing consumer trust—First Alert has been recognized as the most trusted fire safety brand for six consecutive years.
For more detailed information on testing standards and thresholds, refer to guidance from UL Solutions, Intertek, UL Solutions Canada, or Intertek Canada directly.
Frequently Asked Questions
What do certification marks like “UL Listed” or “ETL Listed” mean on a smoke or CO alarm?
Certification marks like UL Listed or ETL Listed indicate that a product has been independently tested by UL Solutions or Intertek to meet specific safety and performance standards. This testing goes beyond manufacturers’ claims and evaluates how the product performs under defined conditions, including safety risks, durability, and functional operation.
What is UL 2034?
UL 2034 is a safety standard for carbon monoxide alarms in the U.S. and Canada that evaluates how alarms respond to different CO concentration levels and exposure times. The standard helps ensure alarms are sensitive enough to provide early warning, while also being designed to reduce false or nuisance alarms caused by short-term or low-level exposure that may not present immediate danger. The CPSC recommends that residential CO alarms comply with the UL 2034 standard.
What is UL 217?
UL 217 is a safety standard for smoke alarms in the U.S. and Canada. UL 217 has undergone major revisions (8th–10th editions) to reflect modern home fire conditions, including increased use of synthetic materials that burn faster and produce more toxic smoke. UL 217 ensures smoke alarms:
- Detect real fires early enough to allow escape
- Perform reliably over their service life
- Avoid nuisance alarms, particularly from cooking aerosols, which often lead occupants to disable alarms
Do all smoke and CO alarms meet the same standards?
No. Different products may be tested to different standards, and certifications can vary by product type and manufacturer. For example, some alarms may only meet basic electrical safety standards, while others also meet additional performance-based requirements for smoke detection sensitivity or carbon monoxide response timing.
Where can I learn more about alarm safety standards?
Visit the official websites for UL Solutions, Intertek, UL Solutions Canada, or Intertek Canada. For additional information about testing and certification programs.