Natural Gas Dispersion Study

Time-based dispersion of methane from a point source leak in the presence of HVAC

With Fire & Risk Alliance, LLC from Rockville, MD, NYSEARCH completed a two-phase study that performed experimental and modeling work to study the dispersion of Natural Gas in residential structures. The data from this project has been provided to industry and the National Fire Protection Agency (NFPA) to aid in the development of a detector placement standard and to facilitate the deployment of methane detectors.

The two-phases of work included over 150 physical tests and modeling simulations to gather data to improve understanding of the gas dispersion patterns in a residence. The overall recommendations from that study are based on a wide array of potential gas flow rates (1 SCFH to 150 SCFH) and release conditions, residential structure configurations and ventilation conditions including HVAC.

Recommendations include:

  1. Sensors should be installed in rooms with gas fire equipment or piping.
  2. Sensors should be installed in sleeping areas or communal areas even if gas fired equipment is not present to account for dispersion due to operation of HVAC.
  3. The LEL threshold for alarm should be 10% LEL. While 25% is still well below the explosive limit the observed delays or lack of detection entirely at the 25% threshold for certain release conditions support moving to a lower threshold that will provide ample notification and alert occupants to a situation that needs to be mitigated.
  4. Whenever possible, sensors should be located within 18” of the ceiling. While receptacle level sensors alarm more frequently with the HVAC system operating, the sensors’ responses are significantly delayed without HVAC operating and at times fail to activate altogether compared to ceiling level sensors.

Computational Fluid Dynamics (CFD) modeling was done as part of the study to simulate high methane leak conditions to map the buildup and the stratification of the gas. The image represents one example of the time-based dispersion of methane from a point source leak in the presence of HVAC. Anything above the black line (area) is in the lower flammability range for the recorded point in time.

For more information Contact NYSEARCH.


For over thirty years, NYSEARCH has worked as a consortium of natural gas Local Distribution Companies (LDCs) who have a common interest and need for research and technology development and demonstration. Today, as part of the Northeast Gas Association (NGA), NYSEARCH manages over (30) projects in various stages of development for LDCs, transmission companies, federal agencies and their manufacturing and commercial partners. NYSEARCH is located in Parsippany, NJ and NGA is headquartered in Needham, Massachusetts.