NFPA 72
Fire alarm lines: what the code asks of the path
NFPA 72 is the national fire alarm and signalling code. For a building owner replacing a copper line, two parts of it matter more than the rest: the requirement that the path to the monitoring station is supervised, and the expectation that whatever equipment replaces the line keeps working when the power does not.
01
What it requires
| Requirement | What that means in practice |
|---|---|
| A supervised communication path | The path to the monitoring station has to be monitored for integrity, so a failure is detected and announced rather than sitting silent until the next inspection. This is the single most important difference between a fire line and an ordinary phone line. |
| Failures annunciated promptly | A path that goes down is expected to raise a trouble signal within a defined period, not at the next test. If you cannot see that a line has failed, the supervision is not doing its job. |
| Standby power on premises equipment | Where shared premises equipment stands in for a telephone line, the current edition sets an expectation of 24 hours of standby power, with a shorter period available only where the fire authority approves a risk analysis. This drives the battery specification, so settle it before hardware is chosen. |
| Restrictions on ordinary internet telephone service | Consumer-grade voice over IP is a known failure mode for alarm dialers: compression corrupts the signalling the panel depends on. The code restricts its use for commercial fire transmission. |
02
Why it matters to your lines
This is why a fire alarm line cannot simply move to whatever is cheapest. A replacement that produces dial tone but loses supervision, or that runs down after four hours in an outage, will not satisfy an inspector and will not protect the building. It is also why fire lines sit in a different price tier from a fax line.
03
Questions worth asking
- Is the path supervised, and how quickly is a failure annunciated?
- How many hours of standby power does the premises equipment hold, and how is that documented?
- Is the traffic carried on a managed voice network or over the public internet?
- What documentation will you hand my inspector at acceptance?
- Has the central station tested and accepted signalling from this equipment?
NFPA 72, National Fire Alarm and Signaling Code