This is the third part of my example design of a fire alarm system for an imaginary new five-story mixed-use building in Plano, Texas.
The previous parts covered the fire alarm requirements for Group A (assembly) and Group B (business) occupancies. This column will focus on the remaining major occupancies in this example: Group M (mercantile), Group R-1 (hotel), and Group R-2 (condos).
Let’s start with the shops.
Group M Requirements
This building has 27,000 square feet of retail – all on the first floor. The International Building Code (IBC) allots 60 sq ft (5.5 sq m) per person for public areas and 300 sq ft (28 sq m) per person for stock and office areas of mercantile occupancies. By rough estimation, let’s count that as 400 public and 10 office/stock occupants.
International Fire Code (IFC) Section 907.2.7 governs fire alarm requirements for Group M. The thresholds are the same as for Group B – a fire alarm system is required when the occupant load exceeds 500 on the first floor or 100 on floors without direct egress.
Other articles in this series
Since our Group M spaces are on the ground level and have fewer than 500 occupants, no fire alarm system would have been required if the retail space alone comprised the whole building. Of course, if you read last month’s column, you know that the retail space’s occupancy will be added to the total occupancy of the mixed-use building.
Group R-1 and R-2 Occupancies
Hotels (Group R-1) and apartments or condos (Group R-2) have slightly different triggers, but both occupancies require fire alarm systems in most multi-story buildings. The specifics depend on the number of units, their location, and how smoke detection is handled.
For R-1, a manual fire alarm system is required unless three conditions are met: two stories max, each unit enclosed by at least one-hour fire partitions, and each unit has direct egress to the outside – such as a one or two-story motel with all the doors on the outside of the building. Our example hotel is on the fifth floor, so the motel exception doesn’t apply.
Furthermore, Section 907.2.8.2 requires smoke detectors in interior corridors serving guest rooms.
Section 907.2.8.3 requires smoke detection in guest rooms, but it doesn’t say that they have to activate all the rest of the alarms in the building. You are even permitted to use single- or multiple-station smoke alarms in guest rooms (i.e., the kind you likely have in your house); however, that isn’t really viable in 2025.
In 2014, NFPA 72 began requiring sleeping area audible notification appliances to emit a 520 Hz tone. Research showed that this low-frequency signal is significantly more effective at waking occupants – especially children, older adults, and people with hearing loss.
The challenge is that generating this tone is energy intensive. Battery-powered smoke alarms – especially those using 9-volt batteries – can’t reliably produce the required waveform at a sufficient volume while maintaining their standby power requirement.
As a result, you cannot meet the sleeping area notification requirement using the built-in sounder on a single- or multiple-station smoke alarm. For all practical purposes, if you are building a hotel today, you need system smoke detectors and system notification appliances inside the guest rooms. That’s the only viable path until manufacturers develop standalone devices that can meet both the audibility and power requirements.
The rules for R-2 occupancies are similar. A fire alarm system is required when the building contains more than 16 units, or if any unit is located on the third floor or higher or below grade. Again, the motel-style exception allows some flexibility, but that doesn’t apply to our example building. The 40,000 square feet of condos on the fourth floor clearly triggers the requirement for a fire alarm system with smoke detection and occupant notification.
CO Detection
Another aspect of residential occupancy requirements in IFC Section 915 is carbon monoxide (CO) detection. Any time you have a residential, educational, or institutional I-1, I-2, or I-4 occupancy with a fuel-fired appliance, you must provide CO detectors and occupant notification.
Common fuels include combustible materials like natural gas, propane, heating oil, and wood. Examples of fuel-fired appliances are water heaters, clothes dryers, stoves, ovens, fryers, and fireplaces.
Internal combustion engines are also significant generators of carbon monoxide, so any building with an attached, closed private garage where someone can then proceed to a sleeping unit or a classroom – or where there are sleeping units or classrooms on the floor immediately above or below the garage – must also have CO detection.
Carbon monoxide poisoning is a serious risk to health and life. I highly recommend reading the extensive requirements in IFC 915.
Coming Up Next
In the next column (July issue), I will introduce high-rise requirements, define what makes a building a high-rise, look at how local amendments can shift that definition, and explore the system requirements that come with the label. As always, feel free to contact me with your questions and clarifications!
