Many building owners working through retrofit or new construction projects are familiar with International Mechanical Code (IMC) standards, which state that an HVAC smoke detector be installed on any air handling system with a capacity greater than 2,000 cubic feet per minute (CFM).

 Following installation of a new air handling system, most building owners will need to have their new heating or ventilation equipment inspected by municipal code authorities, who adhere to requirements put into place by the IMC. A common item flagged on installations of industrial HVAC equipment—including Cambridge Air Systems products—is that a smoke detector was not installed on the system. This is a common request made by engineers and building inspectors that we see at Cambridge Air Solutions – and is a misinterpretation of how our 100-percent outside air make-up air systems and industrial heating products work. Have you ever received a request to include an HVAC smoke detector with your Cambridge heater? You are not alone. Within this article, the experts at Cambridge seek to alleviate any confusion over whether a smoke detector should be installed on your new HVAC system, and why your inspector may have flagged this issue in the first place.

When Are Duct Smoke Detectors Required?

It is true that with most traditional recirculating air distribution systems, installation of an HVAC smoke detector is required. Within Section 606 of the International Mechanical Code (IMC),this requirement is clearly addressed, stating the following: 606.1 Controls required. Air distribution systems shall be equipped with smoke detectors listed and labeled for installation in air distribution systems 606.2 Where required. Smoke detectors shall be installed where indicated in Sections 606.2.1 through 606.2.3. However, the code statement does not end there. It continues: 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. Cambridge Air Solutions systems, including make-up air units, ventilation systems and industrial heaters use only 100-percent outdoor air to heat and ventilate. Because of this design, Cambridge’s air systems are incapable of spreading smoke beyond these parameters. The IMC Commentary provides further explanation on the intent of the code: It is not the intent of Section 606 to require duct smoke detectors in systems that function only as exhaust systems or only as makeup air systems. Remember, a make-up air supply system that discharges 100-percent outdoor air into a building does not withdraw air from the building and, therefore, cannot contribute to the movement of smoke. Because of this important reason, Cambridge units fall under the exception stated in IMC code section 606 and thus do not require an HVAC duct smoke detector system installation.

Why Are There Duct Smoke Detector Requirements?

It is more important to keep in mind that the intended application of Section 606 is to address the potential hazard caused by ducted air distribution systems that link together rooms and spaces within a building, thereby providing the means to distribute smoke to such rooms and spaces. For more traditional systems, which recycle indoor air, the smoke detector requirement is in place to quickly detect smoke coming from one area of a large commercial building and to alert other areas within the large facility. Safety is the key reason why smoke detectors for HVAC systems are often required. Note, that 100-percent outdoor air systems of any type, including Cambridge Air Solutions equipment cannot transport smoke beyond the area of fire origin and are thus exempt from the provisions of this section.

Our Director of Engineering Dave Binz describes how the Cambridge team approaches an industrial retrofit process, and the best way to get started getting answers about your project.