Fire detection, alarm and signaling systems play an important role in industrial fire protection. That role can be one of an upfront starring actor, or it might be more of a supporting role.

Building, fire and life safety codes use different terms to describe occupancies that a lay person would group wholly into the category of "industrial occupancies.” The International Code Council (ICC) family of model codes has a "factory” use group while the National Fire Protection Association (NFPA) family has an "industrial” occupancy. Both have a "storage” category that might also fit the situation.

The ICC codes have limits on the quantities of hazardous materials, which define the point at which a use group (factory, storage or other) becomes a "high hazard” use group. NFPA’s building and life safety codes have similar limits on the quantities of hazardous materials that define when the hazard of the contents warrants additional prevention and protection measures beyond what the base occupancy might be required to have. In other words, in the ICC codes, the quantities and types of materials might change the use group from "factory” or "storage” to high hazard while NFPA codes would retain the occupancy designation, but impose additional requirements.

As with any fire prevention or protection project, new or existing, the engineering team must carefully study and document the process, storage and materials as well as the property characteristics that all affect the code requirements. This article will not try to enumerate what specific codes might require. Instead, it will illustrate detection, alarm and signaling system configurations commonly used in these industrial, factory, storage and high hazard occupancies. It will also introduce some newer applications that are gaining popularity as business owners and insurers seek to further reduce the risk of property and mission interruption losses below the levels afforded by code compliance.

Many, but not all, industrial, factory and storage operations are located in large volume spaces. The high volume provides a large "sink” for heat and smoke and many ways for occupants to move away from fires.

Except for some storage occupancies, the large volume also provides good sight lines for occupants to see fire or smoke long before it directly threatens them or their safe egress from the space. Even in congested, large- volume storage spaces, a hidden fire will likely be smelled by occupants or will activate sprinklers before threatening occupants.

These conditions contribute to long available safe egress times (ASET) relative to the onset of conditions hazardous to the occupants. Without any high hazard conditions or materials, a basic fire alarm system would not be required by most codes to have any occupant notification capability in the building, provided that there was supervision of any required sprinkler systems at an attended location such as a supervising station meeting the requirements of NFPA 72.1

The typical baseline system would monitor sprinkler waterflow switches and sprinkler valve tamper switches. There would be no other automatic fire detection devices and no required occupant notification appliances. An historical provision contained in NFPA 72 would require that such a system have at least one manual fire alarm box (pull station) located as required by the authority having jurisdiction.1 The box provides a way to transmit a fire alarm signal to the supervising station in the event that the sprinkler waterflow switches are taken off-line for testing or maintenance. This presumes that the method used to place the system "on test” leaves the manual fire alarm box in service.

In some jurisdictions, the mechanical codes might require the installation of duct smoke detectors when the supply or return volumetric airflow exceeds certain limits. The return side duct smoke detection is intended to prevent the recirculation of smoke in a building.

In a multistory building, duct smoke detectors are required to be located at the point where the air return joins a common return to the air handler. The detector serving the air return for the fire floor would eventually operate and shut down the system to prevent continued circulation of the smoke-laden air. However, due to dilution rates, there may already have been some recirculation of smoke to the common air handler and back to all floors served by the system.2,3 Occupants on other, non-fire, floors may smell the smoke before the duct smoke detectors will operate.

However, in a large-volume factory or storage space, such as that shown in Figure 1, there might be several rooftop units serving a single, wide-open fire area. Each unit might serve an HVAC zone, or section of the factory floor, without any dividing walls delineating the next HVAC zone.

Figure 1. Building Section

Even if the delay caused by potential smoke stratification is ignored, the delay in the response of a conventional air return duct smoke detector could be considerable due to smoke dilution at the air return point. If there are occupants in the area, they may smell and see smoke before conventional duct smoke detectors operate. Also, in most manufacturing facilities, smoke detection, whether area type or in ducts, would be difficult to access for periodic inspection, testing and maintenance, and would be prone to nuisance activations caused by the normal presence of fumes or particulates. Instead of using duct smoke detectors, one should consider shutting down the air handlers upon activation of any manual fire alarm box or sprinkler waterflow switch.

In certain situations, mission continuity and property protection might warrant additional protection above that provided by automatic sprinklers alone. Examples might include pharmaceutical production and storage, food storage facilities and certain one-of-a-kind production facilities.

Fire detection, alarm and signaling systems can play a vital role in risk reduction by helping to control fires at early stages or by initiating smaller, controlled, manual suppression efforts before fires grow to the size needed to initiate automatic sprinkler operation.4

In high-volume manufacturing and storage spaces, video image smoke and fire detection systems and highly sensitive smoke detection systems using special spot or air-sampling type detectors can be used to provide early detection.5 Projected beam smoke detectors also provide earlier detection than conventional smoke detectors, while being less prone to nuisance sources and easier to access, test and maintain.6 These systems can all be designed and deployed to provide variable signaling that depends on the conditions and the desired responses.7

Signaling systems also serve as the central point for monitoring the status of other critical fire protection and facility infrastructure systems such as private and public water supplies, fire pumps, generators, elevators and process control equipment. Increasingly, they are being integrated with emergency communications systems, mass notification systems and facility paging and information systems. When the design team fully understands the owner’s needs, goals and objectives, a fire detection, alarm and signaling system can be designed as an integral part of the solution that eliminates redundant systems and reduces initial and life cycle system costs.

Robert P. Schifiliti, P.E., FSFPE, is with R.P. Schifiliti Associates, Inc.

Editor’s Note: Robert Schifiliti has been the regular author of the NEMA supplement since it began running in these pages in 2002.


  1. NFPA 72, National Fire Alarm and Signaling Code, National Fire Protection Association, Quincy, MA, 2013.
  2. "The Efficacy of Duct Smoke Detection, Part 1” NEMA Supplement in Fire Protection Engineering, Winter 2006.
  3. "The Efficacy of Duct Smoke Detection, Part 2,” NEMA Supplement in Fire Protection Engineering, Spring 2006.
  4. NFPA 550, Guide to the Fire Safety Concepts Tree, National Fire Protection Association, Quincy, MA, 2012.
  5. Gottuk D. and Dinaburg, J., "Fire Detection in Warehouse Facilities, Final Phase I Report,” Fire Protection Research Foundation, Quincy, MA, 2012.
  6. "Projected Beam Smoke Detectors – More Than Just a Substitute for Spot Detectors,” NEMA Supplement in Fire Protection Engineering, Summer 2004.
  7. "Alarm, Trouble and Supervisory – Degrees of Conditions, Signals and Responses,” NEMA Supplement in Fire Protection Engineering, 4th Quarter 2011.