Smoke Alarm User Manual

Installation, Operation and Maintenance Manual
Page 5-12 Issue 1
February 2001
5.23 Return Air Grill Sampling Design
Return Air Grill Sampling systems are designed with the “SNIFF” Version 3.0 software. The same basic
rules apply with the exception of the point spacing requirements. The return air grill sampling method and
the distributed pipe sampling method can be used in the same detection zone.
Sampling pipes should be centred in the front of the return air grill. Sampling points can be spaced so
that a minimum of three holes is used for each grill. Large grills may require more sampling holes. The
sampling holes should be 90-degrees to the airflow with a closed-ended pipe (capped).
END CAP
AIR FLOW
SAMPLING PIPE
CENTERED ON GRILL
RETURN AIR
GRILL
SAMPLING HOLES POSITIONED
90 TO AIR FLOW
o
*
Figure 5.2 Return Air Grill Sampling Method