By Vincent Powers, ITM Specialist

There are many assumptions regarding air and nitrogen supply for dry pipe and pre-action systems, in this blog we will address the major concerns.

Also, in the spirit of NFPA 13, The Standard for Installation of Sprinkler Systems, the term air will include nitrogen and other approved gas.

First, let’s discuss the NFPA 13 installation requirements for air and air supplies.

We often see on social media and other social platforms that the air supply must be listed. Current, this is not the case, until the 2025 edition of NFPA 13 is adopted, which will require air compressors to be listed. As the industry knows this can have consequences and finally the NFPA 13 committee has addressed this concern in the 2025 edition, Section 7.10 stating that air compressors dedicated to the sprinkler system shall be listed.

Air compressors are an essential piece of equipment for dry and pre-action systems, the reliability and durability of these components is paramount to a properly operating fire sprinkler system. Ensuring that these components will work as needed they must undergo rigorous testing to meet the requirements of UL 1450, Motor-operated air compressors, vacuum pumps, and painting equipment, which includes fire sprinkler system air compressors. Supply chain type compressors and shop air compressors are not held to the same standards as a listed compressor and simply do not provide the same reliability or durability. Sure, they are a great band aids until a listed compressor can be acquired, but they are not in it for the long haul.

Now that is settled, let’s discuss mounting, supply times, air maintenance devices, and a few other items.

Mounting Air Compressors for Pre-Action Systems

There is nothing in NFPA 13 that requires the air compressor to be mounted in any specific fashion, this is a manufacturer requirement. As always, it is a good practice to read the manufacturer’s instructions when installing or maintaining any fire sprinkler component or appurtenance.

Supply Times

NFPA 13 has required the largest system to have the air replenishment within 30 minutes. This does not mean that all systems supplied by a single compressor replenish in 30 minutes but does mean that any single system shall be replenished in this time frame. The only exception to this rule is when the sprinkler system is protecting a space that is 5° F or lower, then the requirement is increased to 60 minutes. This requirement does not change for nitrogen generation systems.

Air Supply Connections

The connection to the sprinkler system shall be no less than ½” in diameter. There is no requirement for this connection to be hard piped or flexible. Many manufacturers will provide a flexible hose of some sort, but this is not a requirement within NFPA 13. I am sure we have seen other hoses installed in systems not manufacturer specifically for this application, such as a garden hose and there is nothing, in NFPA 13 that prohibits this, provided that the hose can withstand the temperature and pressure from the compressor.

Each dry pipe or pre-action system shall have an individual air maintenance device (AMD) but we often see a single AMD installed on multiple systems. This does not meet the requirements of NFPA 13, and something that cannot be addressed by NFPA 25 The Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems. The only exception to the requirement for an AMD is when the air compressor provides less than 5.5 cubic feet per minute of air, then the AMD is not required.

Dedicated Electric

The requirement for the air to have a dedicated electric circuit came in the 2016 edition of NFPA 13 and states that the compressor shall be installed in accordance with NFPA 70, The National Electric Code, article 430.

The 2017 edition of NFPA 25, Section 13.10 is the first edition to require inspection, testing, and maintenance of air compressors and this was expanded on in the 2020 edition. Some of these requirements are pretty standard like inspect for physical damage, wiring is intact (this does not mean on a dedicated circuit), piping is in intact. One that draws my attention is that is requires the inspector to verify the compressor is anchored to the structure or system piping. This is an issue because it is not a requirement of NFPA 13 so technically it does not have to be anchored.

The testing requirements are again, pretty basic, make sure it works by dropping air pressure, ensure it refills the system within 30 minutes and does not overheat.

Like most maintenance items, NFPA 25 says to maintain in accordance with the manufacturer’s instructions and change the oil annually or more frequently if suggested by the manufacturer.

In the end, there are many who have been taught by their supervisor or someone else that was taught by someone else and never really knew what the standards tell us to do. This blog was intended to provide some basic standard requirements for the installation and maintenance of air for dry and pre-action systems.

Have a Question About Air Compressors for Fire Sprinkler Systems? The NFSA Can Help

The NFSA team, consisting of dedicated members and staff, plays a pivotal role in shaping fire protection codes and standards. Our involvement spans over 250 committees, ensuring that we stay informed and influential in the latest industry developments.

One of the key benefits of NFSA membership is our Expert of the Day service, which offers members access to authoritative answers on even the most challenging code and standards queries. Whether you have a question about fire protection codes or need expert advice on air compressors, our team is here to assist you with the knowledge and support you need.