Fill in once; every calculator uses it and prints it with the results. Stored only on your device.
Fire alarm: number of smoke and heat detectors
Enter the room size, ceiling height and detector type. The tool lays out a detector grid at maximum spacing, checks coverage and gives detectors per room and in total.
Quick answer
Smoke detector, 4.0 m ceiling: 12 per room (grid 4 × 3, about 7.5 × 6.7 m apart), 12 in total.
Preliminary results
Per room12pcs
Total detectors12pcs
Grid4 × 3
Actual spacing7.5 × 6.7m
| Step | Result | Basis |
|---|---|---|
| Table by ceiling heighth = 4.0 m ≤ 6.0 m | 70 m² · 8.5 m · 4.0 m | TCVN 5738:2021 ⚠ |
| Grid by spacingn = 1 + ⌈(L − 2×4.0)/8.5⌉; L = 30.0, 20.0 m | 4 × 3 | TCVN 5738:2021 ⚠ |
| Coverage per detector7.5 × 6.7 ≤ 70 m² | 50.0 m² | TCVN 5738:2021 ⚠ |
| Minimum per roommax(12; 2) | 12 pcs | TCVN 5738:2021 ⚠ |
| Total detectors12 × 1 | 12 pcs | — |
- Manual call points at exits and stair landings, 0.8–1.5 m high, ≤ 50 m apart indoors ⚠.
- Each zone covers ≤ 2,000 m² open area or ≤ 500 m² enclosed; up to 20 rooms on one floor sharing a corridor, each with a door indicator ⚠.
- Beams, raised floors and ceiling voids over 0.4 m are treated as separate cells.
Sources and assumptions. Coverage and spacing of point detectors per TCVN 5738:2021 (equivalent to SP 5.13130); at least 2 detectors per room without a confirmation algorithm ⚠. Preliminary count for a rectangular room with a flat ceiling. ⚠ = code table value to be checked against the original standard. Preliminary results for material selection and budgeting; not a substitute for an approved fire protection design.
Suggested materials
Smoke detector (with base)12 pcs
Manual call pointper drawing
Fire bell, sounder-beaconper drawing
Fire alarm control panel1
Fire-resistant signal cable 2 × 1.0 mm²per drawing
Coverage and spacing of point detectors
| Type | Mounting height | Area ≤ | Between ≤ | To wall ≤ |
|---|---|---|---|---|
| Smoke detector | ≤ 3.5 m | 85 m² | 9.0 m | 4.5 m |
| Smoke detector | 3.5–6.0 m | 70 m² | 8.5 m | 4.0 m |
| Smoke detector | 6.0–10.0 m | 65 m² | 8.0 m | 4.0 m |
| Smoke detector | 10.0–12.0 m | 55 m² | 7.5 m | 3.5 m |
| Heat detector | ≤ 3.5 m | 25 m² | 5.0 m | 2.5 m |
| Heat detector | 3.5–6.0 m | 20 m² | 4.5 m | 2.0 m |
| Heat detector | 6.0–9.0 m | 15 m² | 4.0 m | 2.0 m |
Frequently asked questions
How many m² does one smoke detector cover?
Ceilings up to 3.5 m: up to 85 m², detectors ≤ 9 m apart and ≤ 4.5 m from walls. Higher ceilings reduce coverage (55 m² at 12 m).
Does a 10 m² room need 2 detectors?
By the standard's principle each room has at least 2 detectors to avoid false alarms and single-point failure ⚠; addressable systems with a confirmation algorithm may use 1 per approved design.
Smoke or heat detector in a kitchen?
Kitchens, steamy or dusty rooms use heat detectors to avoid false alarms; heat detectors cover less (25 m² at ≤ 3.5 m).