Procedure for Puff Testing For Gas Suspression?

9/17/2025

Has anyone ever conducted puff testing for a gas fire suppression system?

The owner is requiring us to perform this test, but I have never done it on previous projects. I checked NFPA 2001, and its requirements for flow testing are not detailed enough.

I would like to know the specific procedures for conducting this test, as well as the key considerations to keep in mind. Ideally, I'd like to find a specification document or procedure to follow. Advance Thanks！

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5 Comments

Glenn Berger

9/17/2025 08:12:33 am

Depending on what is being called the puff test --

I have been involved with projects, while the room is pressurized using the smoke pencil to identify where there are leaks.

Bob Ballard

9/17/2025 08:33:14 am

I have performed puff tests on gas fire suppression systems. The specific detailed procedures you're looking for should be found in the manufacturer's Design, Installation, Operation, and Maintenance (DIOM) manual for your particular clean agent system. Each manufacturer typically provides its own step-by-step puff test procedures, which are more detailed than those found in NFPA 2001.

NFPA 2001 Requirements Summary:

Main Body:
Section 10.4.15 - States that "a flow test using nitrogen or inert gas shall be performed on the piping network to verify that flow is continuous."

Appendix:
Section A.10.4.15 provides additional clarification:

The purpose is to conduct a short-duration "puff test" through the piping network
Determines that flow is continuous and checks valve orientations per system documentation
Use gaseous nitrogen or inert gas at a pressure not exceeding the normal system operating pressure
Gas should be introduced at the clean agent container connection
Visual indicators must verify that gas has discharged from each and every nozzle

The NFPA standard provides the requirements and basic parameters, but the manufacturer's DIOM will give you the specific procedural steps, equipment needed, safety precautions, and documentation requirements. I'd recommend starting there and coordinating with your system manufacturer's technical support if you need additional guidance.

Jose R Figueroa

9/17/2025 09:25:46 am

Refer to Factory Mutual DS 4-9

The NFPA 2001 standard briefly mentions puff testing in Chapter 10 (Section 10.4.15) to verify unobstructed flow using inert gas without a complete discharge.

DS 4-9 details the design, installation, inspection, testing, and maintenance of clean agent systems like FM-200 and Novec 1230, focusing on system reliability when full discharges are not feasible due to cost or environmental concerns.

Why Conduct a Puff Test? The puff test verifies the integrity and unobstructed flow of discharge piping, nozzles, and valves, confirming that gas can flow continuously without blockages. FM DS 4-9 highlights that inadequate flow verification can lead to property damage or safety hazards. When full discharge tests are avoided, puff tests serve as a non-destructive alternative to ensure operational readiness.

When to Conduct a Puff Test?
- New Installations: After piping assembly and before any full discharge testing.
- Modifications or Repairs: After changes to piping, nozzles, or valves.

Testing Sequence: Conduct hydrostatic testing first, then the puff test, followed by enclosure integrity tests.

Method: Use nitrogen or inert gas at normal operating pressure, observing flow at nozzles for 1-2 minutes.

Pre-Test Preparation: Ensure piping is cleaned and valves are correctly positioned.

Acceptance Criteria: Continuous flow from every nozzle with no pressure drops.

Documentation: Record results, including pressures and observations, as part of the acceptance certificate.

If this is an FM Insured location, consult FM Engineering before testing for additional compliance procedures.

Mark Harris

9/17/2025 11:28:10 am

Great summaries Bob and Jose. Depending on what was available at time of test I have seen both air compressor and a nitrogen tank supply used. Have also seen balloons stretched over nozzles. At least for brands I dealt with don't recall manufacturer manuals having much more detail than NFPA 2001.

Jose I am curious where you came up with one to two minutes? Not sure if that long would be required to find blockage.

As I recall NFPA 2001 does have an exception with limited pipe and fittings and often system installs are riser pipe to a single nozzle that fell under the exception.

Jose R Figueroa

9/17/2025 11:58:14 am

Hi Mark, Thank you! I referenced and overly abbreviated “fluttering ribbons or smoke tracers,” “cylinder discharge port,” and “1-2 minutes per branch,” are common industry practices.

The quoted description of the puff test method is a summarized and elaborated version based on the guidelines in FM DS 4-9 (revised September 2023). The closest matching content appears in Section 2.5.1.5.3 on page 11, which states:
“For systems that have not been subjected to a full discharge test, conduct a flow test (i.e., a ‘puff test’) using nitrogen or an inert gas on the piping network to verify flow is continuous and the piping and nozzles are unobstructed. Refer to Section 2.3.2.5 to best ensure this unobstructed flow condition. A. Conduct the test at a pressure not exceeding the system’s normal operating pressure. B. Conduct the test for a time period that allows verification of unobstructed flow from all nozzles. C. If discharging into a sensitive occupancy (e.g., a computer room), cover the nozzles with a sock or similar material to prevent potential discharge of debris into the room. D. If obstructed flow is observed during the puff test, or trapped debris is identified by visual inspection of the nozzles and dirt trap following the test, remove, clear, and reinstall the nozzle and dirt trap.”

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Procedure for Puff Testing For Gas Suspression?

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