Duct smoke detectors should be located in
the hvac area between 6 and 10 duct-equivalent diameters of straight, uninterrupted run
. The International Mechanical Code section, 606.2.
Do duct detectors go on the supply or return?
NFPA 90A requires duct detectors to be installed
on the supply side
of air handler units with airflows of more than 2,000 cubic feet per minute (cfm). The standard also requires a duct detector on the return side of any unit with air flows exceeding 15,000 cfm and which serve more than one floor of a building.
How far does a smoke detector have to be from a vent?
NFPA 72 recommends that they should not be installed
closer than 3 feet
from any supply air diffuser or return vent. If they are too close to the supply, smoke may not reach the detector. Also, the air coming out of the vent contains dust and dirt, which can settle in the detector and cause nuisance alarms.
Where do you put a duct smoke detector?
Installation guidelines
Install the duct smoke detector
on a flat section of HVAC duct between six and ten duct widths from any bends or obstructions
. Install supply-side detectors at a point downstream from the supply fan and after the air filter.
How does a duct smoke detector work?
How Do They Work? Duct detectors
sample currents in the air handling equipment to determine if smoke or fumes are present
. If smoke is detected, the device will close dampers, stop fans and blowers, and trigger an audible and visible signal at the fire control panel, Kapparos explains.
What CFM requires a duct detector?
NFPA 90A and International Mechanical Code
The International Mechanical Code requires a duct smoke detector in the return for units
over 2000 cfm
and requires a detector in the supply duct for systems over 15,000 cfm.
What is the largest return air opening that can be protected with a single smoke detector?
Smoke detectors shall be installed in return air systems with a design capacity greater
than 2,000 cfm (0.9 m
3
/s)
, in the return air duct or plenum upstream of any filters, exhaust air connections, outdoor air connections, or decontamination equipment and appliances.
Should smoke detectors be on wall or ceiling?
Smoke alarms should be mounted in or near bedrooms and living areas,
either on the ceiling or the wall
. Ceiling mounting it is typically preferred as it allows the smoke alarm to be placed more centrally in the room.
Where should smoke alarms not be placed?
Where the temperatures are regularly below 40°F (4° C) or above 100° F (38° C) including unheated buildings, outdoor rooms, porches, or unfinished attics or basements. In very dusty, dirty, or greasy areas. Do not install a Smoke Alarm directly over the
stove
or range.
How close should a smoke detector be to a bedroom door?
A smoke detector on each level – excluding crawl spaces and unfinished attics – one inside each sleeping room, and one outside each sleeping area (
within 21 feet of
the bedroom doors) provided pretty good coverage for most homes.
Which is the primary purpose of duct detectors?
The primary purpose of duct smoke detection is
to prevent injury, panic, and property damage by reducing the spread (recirculation) of smoke
. The detector samples air currents passing through a duct and gives dependable performance for management of smoke and combination fire smoke dampers.
How do you clean duct smoke detectors?
To clean the duct smoke detector:
Remove the detector’s cover then power down the detector by disconnecting the initiating device circuit wiring
. 2. Using a vacuum cleaner, clean compressed air, or a soft bristle brush, remove loose dirt and debris from inside the detector housing and cover.
How do you test a duct smoke detector?
Spray aerosol smoke* into the duct through the 1⁄4 inch hole for five seconds.
Wait two minutes for the duct smoke detector to alarm
. If the duct smoke detector alarms, air is flowing through the detector.
Do duct detectors need to be monitored?
Bottom line is if a building fire alarm system is not installed, duct smoke detectors shall be stand alone and
are not required to be connected/monitored by a dedicated function fire alarm system
.
Are duct smoke detectors required on exhaust fans?
Return system smoke detectors are not required where the entire space served by the air distribution system is protected by a system of area smoke detectors.
Smoke detectors are not required in exhaust ducts
.
What primarily determines the installation of smoke duct detectors?
In short, there’s two prevailing standards that determine whether duct detection is required. The first (and most common in the United States), is
the International Mechanical Code (IMC)
. Section 606.2 identifies areas where smoke detection is required for the purpose of mechanical unit shutdown.
