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17.7.6 Special Considerations
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Combination and multi-sensor smoke detectors that have a fixed-temperature element as part of the unit shall be selected in accordance with Table 17.6.2.1 for the maximum ceiling temperature expected in service.
The location and spacing of smoke detectors for high-rack storage shall address the commodity, quantity, and configuration of the rack storage.
The purpose and scope of 17.7.6.3 shall be to provide location and spacing guidance for smoke detectors intended for early warning of fire in high air movement areas.
Smoke detectors shall not be located directly in the airstream of supply registers.
Smoke detector spacing shall be reduced where the airflow in a defined space exceeds 8 minutes per air change (total space volume) (equal to 7.5 air changes per hour).
Where spacing must be adjusted for airflow, spot-type smoke detector spacing shall be adjusted in accordance with Table 17.7.6.3.3.2 or Figure 17.7.6.3.3.2 before making any other spacing adjustments required by this Code.
Table 17.7.6.3.3.2 Smoke Detector Spacing Based on Air Movement (Not to Be Used for Under-Floor or Above-Ceiling Spaces)
| Minutes per Air Change | Air Changes per Hour | Spacing per Detector | |
|---|---|---|---|
| ft2 | m2 | ||
| 1 | 60 | 125 | 12 |
| 2 | 30 | 250 | 23 |
| 3 | 20 | 375 | 35 |
| 4 | 15 | 500 | 46 |
| 5 | 12 | 625 | 58 |
| 6 | 10 | 750 | 70 |
| 7 | 8.6 | 875 | 81 |
| 8 | 7.5 | 900 | 84 |
| 9 | 6.7 | 900 | 84 |
| 10 | 6 | 900 | 84 |
FIGURE 17.7.6.3.3.2 High Air Movement Areas (Not to Be Used for Under-Floor or Above-Ceiling Spaces).
Air sampling or projected beam smoke detectors shall be installed in accordance with the manufacturer's published instructions.
Where HVAC mechanical rooms are used as an air plenum for return air, the spacings of smoke detectors shall not be required to be reduced based areas. on the number of air changes.