Fire detection and alarm (FD&A) systems play a critical role in protecting life, property and business continuity. Smoke detectors, heat detectors, manual call points and alarm devices are often the first line of defence, providing early warning and enabling timely evacuation or intervention. However, like all safety-critical systems, their effectiveness depends on continued reliability, suitability for the environment and proper maintenance.
While it is widely assumed that fire alarm systems should simply be replaced after a fixed period, the reality is more nuanced. There is no single defined lifespan for all fire detection and alarm components, as performance depends on technology, environment, usage and manufacturer recommendations. What matters most is whether the system remains reliable and fit for purpose.

Below are the key indicators that replacement should be considered.

Age of the System or Devices
There is no mandatory “end of life” age defined in BS 5839-1, the code of practice for fire detection and fire alarm systems. Different technologies and components age at different rates. Manufacturers are best placed to advise on the expected lifespan of specific products, and some components—such as CO detectors—do have clearly defined replacement periods.

That said, age becomes a concern where faults, failures or obsolescence increase over time. If detectors or control equipment are becoming unreliable, difficult to source spares for, or unsupported by the manufacturer, a planned replacement may be more appropriate than reactive repair.
Environmental conditions are also critical. Detectors installed in dusty, dirty or harsh environments will generally deteriorate faster than those in clean, controlled spaces, regardless of age.

Reduced or Distorted Sound Output
Alarm devices must produce a clear, audible warning. If sounders are muffled, distorted or noticeably quieter, this may indicate internal degradation, contamination or wear—particularly in devices that have experienced frequent or prolonged operation.
FIA guidance notes that while occasional testing has little impact, extended or repeated operation can reduce the performance of some alarm devices over time, especially mechanical bells or certain visual alarm technologies. Any reduction in output should be investigated promptly and may justify replacement.

Persistent Beeping or Fault Indications
Intermittent beeping often indicates a low or failing battery. Standby batteries for control equipment typically have a life expectancy of around four years, while batteries for wireless devices may require replacement more frequently, depending on duty cycle and manufacturer guidance.
However, persistent fault indications can also suggest age-related failure or component degradation. Where faults are recurrent and clearly linked to ageing equipment, continued maintenance may no longer be the most effective or reliable solution.

Frequent False Alarms
Unwanted fire signals are not merely inconvenient—they can undermine confidence in the system and lead to dangerous complacency. FIA guidance is clear that systems generating frequent false alarms risk becoming ineffective, potentially failing to meet fire safety legislation requirements.
Age-related sensor degradation, environmental contamination or unsuitable detector types are common causes. Where false alarms persist despite appropriate maintenance and adjustment, replacement or system redesign should be considered.

Visible Deterioration or Damage
Physical condition remains an important indicator. Cracks, corrosion, heavy contamination or discolouration can all compromise performance. Corrosion may arise from environmental moisture or battery leakage, while heavy dust ingress can affect detector sensitivity.
Although some components—such as manual call points and heat detectors—are generally robust and may remain serviceable for extended periods, visible damage should always prompt further assessment by a competent person.

Actions to Maintain Reliability
To ensure continued protection and compliance:
•    Test fire alarm systems regularly in accordance with BS 5839-1
•    Replace batteries in line with manufacturer and standard recommendations
•    Clean detectors periodically, particularly in environments prone to dust or contamination
•    Monitor fault trends and false alarms for signs of age-related deterioration
•    Consider planned replacement where spares, support or reliability can no longer be assured
•    Ensure systems are installed, maintained and reviewed by third-party certificated companies (e.g. LPS 1014 or SP203-1)

Final Thought
Fire detection and fire alarm systems do not simply “expire” on a set date. Instead, reliability, environmental suitability and ongoing performance should guide decisions about repair or replacement. A system that can no longer be trusted to operate correctly—whether due to age, faults or false alarms—ceases to provide meaningful protection.
If in doubt, seek advice from a competent professional who can assess whether your system remains fit for purpose or whether a planned upgrade would better protect lives and premises.