In an emergency, every second counts. One of the most critical features of your fire safety system is the audibility of the fire alarm.
It’s not enough for your alarm system to simply be installed and maintained—it also needs to be loud enough to warn every person in the building, regardless of where they are or what they’re doing.
So how loud should a fire alarm be in a commercial building? Let’s take a look.
The Legal Framework and Standards
The key standard for fire alarm systems in commercial premises is BS 5839-1:2017, which sets out the code of practice for the design, installation, commissioning and maintenance of fire detection and alarm systems in non-domestic buildings.
According to BS 5839-1, the fire alarm sounders must:
- Be clearly audible in all areas of the building where people are likely to be present
- Have a minimum volume of 65 decibels (dB) or 5 dB above the ambient background noise—whichever is higher
- Be 75 dB at the bedhead in sleeping areas if the building is used for overnight stays
This means the alarm should cut through normal working conditions—whether that’s a quiet office or a noisy factory floor.
What Does That Sound Like?
To put it in context:
- 60 dB = normal conversation
- 70 dB = vacuum cleaner
- 80 dB = busy traffic or power tools
So, for a typical commercial setting, your fire alarm needs to be significantly louder than the usual noise levels. If your workplace is particularly noisy (for example, a manufacturing floor or commercial kitchen), your fire alarm will need to exceed 80 or even 90 dB in those areas.
Why Ambient Noise Levels Matter
One of the most important aspects of fire alarm design is measuring background noise throughout the building. This includes:
- Machinery or equipment
- HVAC systems
- Radios, telephones, or background music
- People talking or working in groups
BS 5839-1 requires that the alarm sound level is at least 5 dB above the typical ambient noise for each location in the building. In high-noise environments, visual alarms (beacons) may also be required as an additional warning method.
Where Alarm Sounders Should Be Located
To ensure even sound distribution, fire alarm sounders (audible devices) must be placed strategically throughout the building. Common placements include:
- In corridors and stairwells
- In large open-plan offices or commercial areas
- Near entrances, exits, and communal areas
- In individual rooms where staff or customers may be isolated
In areas where high sound levels are needed, multiple sounders or higher output devices may be installed. Sounder placement should be based on a fire risk assessment and acoustic survey, ensuring no dead zones are left uncovered.
Testing and Commissioning
When a fire alarm system is commissioned, the sound levels must be tested and recorded to ensure compliance with BS 5839-1. This includes:
- Verifying the minimum dB level is met in all occupied areas
- Checking that sounders are free from obstruction
- Ensuring sound is distinguishable from other warning systems (e.g. security alarms)
If your commercial building has areas with fluctuating noise levels (like a workshop that’s sometimes silent and sometimes very loud), a variable-level alarm or backup visual alert may be recommended.
Staff and Occupant Considerations
You should also think about who’s in the building:
- Staff wearing hearing protection or in noisy environments may not hear the alarm
- Visitors unfamiliar with the layout need a clear signal to exit
- Disabled occupants may require visual alerts or vibrating pads for effective warning
Your fire risk assessment should consider all of these factors when determining whether the fire alarm system is fit for purpose.
How ESI Can Help
At ESI: Electrical Safety Inspections, we help businesses across Farnborough, Camberley, Reading, Guildford, and the wider Hampshire, Surrey, and Berkshire area design, install, and maintain fire alarm systems that meet the latest British Standards.
We can:
- Carry out sound level checks and identify non-compliant areas
- Upgrade or reposition sounders for maximum coverage
- Add visual indicators where needed
- Support you with fire risk assessments and system servicing
If you’re not sure whether your fire alarm is loud enough—or if your building has changed use or layout—it’s time for a professional check. Contact the team at ESI and we’ll help you ensure your alarm system is ready to protect lives when it matters most.
