• Smoke alarms and detectors work well, but their standards need to be updated to continue to be effective in modern buildings.
• NIST research led to new, better standards for smoke alarms and detectors.
• These advancements are likely to reduce fire severity and save lives.

Smoke alarms are one of the most effective technologies for reducing death, injury, and property damage from fires. Ever since they were introduced in the 1970s, NIST has played a large role in the research that shows that they work and how best to use them.

But homes have changed a lot since the 1970s and so has the typical house fire. Open floor plans have become more common, the mass of flammable material has increased, and flammable foam padding has become more prevalent.

NIST wanted to see if smoke detectors were still effective given the changing conditions for house fires.

In 2004, NIST staff members ran a series of tests on off-the-shelf smoke alarms. In the larger tests, they burned actual furniture in real houses. They carefully took a wide range of measurements, including temperature, smoke obscuration, and gas concentrations. This data was useful for understanding how modern materials burn and whether smoke alarm effectiveness had changed over time.  

One of their surprising findings was that available escape times were far shorter than in the original smoke alarm tests in the 1970s. For example, the average time available for escape from a flaming fire decreased from 17 minutes down to only three minutes. Those lost 14 minutes could make all the difference in a fire.

It was clear that the standards would need to be updated.

What is a standard?

A standard is a set of minimum requirements for how a product should function. The standards for smoke alarms and smoke detectors are maintained by a private organization called UL Standards and Engagement (ULSE).

Alarms and detectors are slightly different, and each has its own standard. Smoke alarms are self-contained devices that sense a fire and sound an alarm; these are typically installed in homes, and must meet the standards outlined in ANSI/UL 217. Smoke detectors sense a fire and send a signal to a central location in a building; the central panel broadcasts the alarm. Detectors are more commonly used in commercial buildings and multi-unit dwellings, and must meet the standards outlined in ANSI/UL 268.

These standards are written for manufacturers. So, if you make one of these devices, you need to ensure that it has been tested and meets the certification requirements in the standard.

ULSE selects the tests and the certification criteria that go into the standard. It bases its decisions on the deliberations of a group of experts, manufacturers, and researchers, including NIST staff.

Raising the bar for alarms and detectors

By 2008, the UL 217/268 Standards Technical Panel had formed a task group to discuss new fire tests and standards for a new generation of fire sensing.  

NIST joined forces with the Consumer Product Safety Commission, the United States Fire Administration, the Centers for Disease Control and Prevention, the Department of Housing and Urban Development, ULSE, the National Fire Protection Association, the National Research Council Canada, the University of Maryland, and the smoke alarm manufacturers to guide these deliberations.  

One of the major concerns they wanted to address in the new standards was the change in common types of smoke. ULSE found that the smoke from burning foam padding in furniture and beds was different from the smoke generated by the fuels used to certify the 1970s devices. The task group also wanted the new devices to detect the fire when it was smaller and made less smoke.  

Detecting the fires sooner is good in general, but it has the potentially bad side effect of increasing the frequency of “nuisance alarms,” alarms due to something other than a fire. Most of these nuisances are caused by cooking. These are a problem for fire safety because they can cause frustrated homeowners to deactivate or ignore their alarms.  

With these goals in mind, NIST conducted more research to come up with recommendations on how to increase the detection of flaming and smoldering fires typical in homes while not also increasing detection of nuisance sources.

The Standards Technical Panel used this research to arrive at a set of three new tests for measuring the sensitivity of a new generation of smoke alarm designs:

• Flaming of a flexible polyurethane foam (FPUF).  
• Smoldering of the same FPUF.
• Broiling of two frozen hamburger patties.

Each of these tests takes place in a certified laboratory. To pass the first two tests, the alarm needs to detect smoke from the burning foam. To pass the final test, the alarm needs to not go off when the hamburgers are cooked. The standards for both alarms and detectors would use the same tests and criteria. NIST’s role as an unbiased source of research was instrumental in gaining approval of the changes.

In 2016, NIST wanted to see if the new standards would actually make smoke alarms better. They ran a group of older smoke alarms through the new tests for the standards and showed that none of the old alarms could pass all of them. This proved that updating the standards was worthwhile.  

Smoke Alarm vs. Bacon

The latest versions of the standards, ANSI/UL 217 8th edition and ANSI/UL 268 7th edition, contain these new tests. Both standards went into effect as of June 30, 2024.

Over time, these new devices will replace the old versions, ensuring that alarms and detectors continue to effectively protect people from fires. 

Additional Reading:

NFPA article: Smoke Alarms in U.S. Home Fires, 2024.  

NIST report: Performance of Home Smoke Alarms: Analysis of the Response of Several Available Technologies in Residential Fire Settings, 2007.

Journal article: An Analysis of the Performance of Smoke Alarms. Fire Safety Science, 2011.

NIST report: Smoke Alarm Performance in Kitchen Fires and Nuisance Alarm Scenarios, 2013.  

Journal article: Performance of Dual Photoelectric/Ionization Smoke Alarms in Full-Scale Fire Tests. Fire Technology, 2010.  

NIST report: Improving Smoke Alarm Performance – Justification for New Smoldering and Flaming Test Performance Criteria, 2014.  

ANSI/UL standard: ANSI/UL 217, Safety Standard for Single- and Multiple-Station Smoke Detectors, 2024.

NIST report: A Study on the Performance of Current Smoke Alarms to the New Fire and Nuisance Tests Prescribed in ANSI/UL 217-2015, 2016.