UPDATE: 780 CMR 10th Edition: Smoke Alarm Changes & Low-Frequency Requirements

With the adoption of the 10th Edition of 780 CMR (Massachusetts State Building Code), Massachusetts has incorporated significant updates tied to the 2021 International Building Code (IBC) and NFPA 72 that impact how smoke alarms and audible notification must be provided in residential occupancies — especially condominium and multi-family buildings.

One requirement in particular — the low-frequency (520 Hz) alarm signal — is driving design changes, cost impacts, and compliance challenges that many stakeholders don’t yet fully appreciate.

Why 520 Hz Low-Frequency Matters

Decades of research show that low-frequency (~520 Hz) alarm tones are more effective at waking sleeping occupants than traditional high-frequency smoke alarm tones. This has resulted in changes to requirements in recent editions of NFPA 72 and the International Building Code (IBC).

What Changed from the 9th to the 10th Edition of 780 CMR

Prior to the 10^th Edition, most apartment and condominium systems have utilized a combination of “system smoke detectors” in common areas and “house powered smoke alarms” inside the units themselves. The following outlines the differences between these terms:

System smoke detectors are low-voltage devices connected to the fire alarm system. They send an alarm signal to the fire alarm panel, that then initiates an evacuation signal.

Smoke alarms are 120-volt devices with internal speakers that most people are familiar with from their home.

Under the 9^th Edition of 780 CMR, in condos and apartments:

System smokes would be located in common areas and in-unit notification of a building alarm would be provided by separate low frequency speakers.

Smoke alarms would be located within the units as in a single-family home. These devices were not technically part of the fire alarm system and were for local notification only.

While the fire alarm system required low-frequency notification in the units for a general alarm, smoke alarms inside the units were not required to be low-frequency. However, that all changed in the 10^th Edition and now smoke alarms are also required to be low-frequency devices.

The core issue this raises is that until very recently there there have been no 120-volt smoke alarm devices, available on the market, that produce a low-frequency alarm. The code is clear that this lack of an available option does not alleviate the designer or installer to meet the low-frequency signal.

First, it’s important to understand why this change is being made. Recent studies have shown that low-frequency signals are six times more effective than the standard smoke alarm in waking people over 65, people with hearing loss, children, and people who are alcohol impaired.

That means, until the market produces such a device, smoke alarms are not permitted to be installed in any jurisdiction that adopts the 2021 International Building Code (IBC). This includes Massachusetts and over 30 other states. So, what are the design options under this revised standard?

First, any such design must incorporate an addressable fire alarm system. Then, to achieve compliant, local notification, designers have three (3) options:

System smoke detectors with low-frequency sounder bases (like a typical hotel design)
System smoke detectors with addressable notification (manufacturer specific)
System smoke detectors with dedicated notification appliance circuits (unlikely to be ideal)

While these changes will improve system notification, they will drive installation costs due to increased device costs and programming time. Permitting will be a challenge as battery calculations will become more cumbersome. After installation, maintenance and testing costs will also increase and access to tenant spaces will have to be coordinated. Additionally, this change will increase the frequency of owner notification and expose the signaling line circuit to trouble alarms from tenants removing detectors or attempting to disconnect them.

However, Gentex has released a new line of products called Gentex “place” series. They offer multiple models that can provide smoke, CO, natural gas, and heat detection. They are UL 217 (9^th Edition) listed, as required by the IBC. Be aware that Gentex states that only Energizer Ultimate Lithium AA (L91) batteries be used. Each detector requires two batteries. These batteries are more expensive and should be a consideration but, compared to the downsides of the other options, it is still likely preferable. As these are new products, make sure your local jurisdiction is comfortable with their use due to these limitations.