What is this duct mounted gizmo?

[Jim Luttrall]

I found this at a Dr. office today. Due to paint over-spray nothing was legible on the cover. It is mounted on the return air side prior to the disposable filter rack. It was only on two of the four units. I'm leaning toward some sort of UV treatment or the like. Anyone familiar with it?
Ignore the complete AHU, loaded it by mistake and can't figure how to delete.
28287

[Ken Santell]

Use goof off on plastic to remove paint. Get a number, scan tag, or brand

[Scott Patterson]

Yep, smoke detector. This type has a shorter lifespan and only work if air is being drawn through the system. For this reason they are not the best option!

[Rick Cantrell]

... This type has a shorter lifespan and only work if air is being drawn through the system. For this reason they are not the best option!

What do you think would be a better option? Why?

[Scott Patterson]

What do you think would be a better option? Why?

Any of the photo electric type detectors that can be mounted on walls or ceilings. They detect a smoldering fire better which produce more CO.

Duct type detectors are good in commercial systems that are alwys on and drawing air for the detector to detect smoke.

[Jim Luttrall]

Ok, makes sense. Kind of weird they had it only on two of the 4 systems though.
New construction of a 5000' Doctors office with full alarm and sprinkler system. I did call for it to be cleaned off and serviced since the filters were full of sheet rock dust and this sensor was before the filter.
Thanks Guys!

[Rick Cantrell]

Wall/ceiling mounted detectors warn the occupants of smoke (fire).
A duct detector slows down the spread of smoke throughout the building.
They are not used instead of wall/ceiling detectors, but are an addition to the system.
So, for what they are used for (stopping the spread of smoke) duct detectors are the best option.

[Scott Patterson]

Rick is talking about the detectors shutting down the system/air handlers when they detect smoke. This is the norm for a commercial system.

[David Bell]

A quick glance at that install shows a pan drain not connected, Improper hanging of unit.

[Henry Henchal]

Typically the commercial mechanical code only requires duct detection on units with a cfm in excess of 2000 cfm...possible the other two units are smaller.

[Tom Rees]

I don't do much commercial but good info here. Thanks guys!!:D

[Joe Funderburk]

Typically the commercial mechanical code only requires duct detection on units with a cfm in excess of 2000 cfm...possible the other two units are smaller.

Correct. Which I've been told is equivalent to 60,000 BTUs.

- - - Updated - - -


Any of the photo electric type detectors that can be mounted on walls or ceilings. They detect a smoldering fire better which produce more CO.

Conventional smoke alarms are not required in commercial buildings without a fire protection system.

[Gregory Booth]

Ok, makes sense. Kind of weird they had it only on two of the 4 systems though.
New construction of a 5000' Doctors office with full alarm and sprinkler system. I did call for it to be cleaned off and serviced since the filters were full of sheet rock dust and this sensor was before the filter.
Thanks Guys!
...........if the building has any procedure rooms, the two units with detectors are supply units and the other two units may be the return (exhaust ) units. Pretty common to have 100% fresh-air systems in medical facilities..........Greg.

[Jim Luttrall]

...........if the building has any procedure rooms, the two units with detectors are supply units and the other two units may be the return (exhaust ) units. Pretty common to have 100% fresh-air systems in medical facilities..........Greg.

They did have the procedure rooms on a separate system but all are typical units of the same size.
The smoke detectors were on the units which served the office and waiting area as well as the proceedure rooms.

[Joe Funderburk]

2012 IMC (does not apply to residential buildings-1 and 2 family dwellings)

DETECTION SYSTEMS CONTROL

606.1 Controls required. Air distribution systems shall be
equipped with smoke detectors listed and labeled for installation
in air distribution systems, as required by this section.
Duct smoke detectors shall comply with UL 268A. Other
smoke detectors shall comply with UL 268.

606.2 Where required. Smoke detectors shall be installed
where indicated in Sections 606.2.1 through 606.2.3.
Exception: Smoke detectors shall not be required where
air distribution systems are incapable of spreading smoke
beyond the enclosing walls, floors and ceilings of the
room or space in which the smoke is generated.

606.2.1 Return air systems. Smoke detectors shall be
installed in return air systems with a design capacity
greater than 2,000 cfm (0.9 m3/s), in the return air duct or
plenum upstream of any filters, exhaust air connections,
outdoor air connections, or decontamination equipment
and appliances.

Exception: Smoke detectors are not required in the
return air system where all portions of the building
served by the air distribution system are protected by
area smoke detectors connected to a fire alarm system
in accordance with the International Fire Code. The
area smoke detection system shall comply with Section
606.4.