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Helium Dispersion in an Attached Single-Car Residential Garage with and Without Vehicle



William M. Pitts, Jiann C. Yang, Marco G. Fernandez, Kuldeep R. Prasad


The dispersion and loss of helium inside a single-car residential garage attached to a single-family house was experimentally characterized by recording time-resolved helium concentrations at multiple locations in the garage and at a single location in the house during and following helium releases near the floor of the garage. Helium served as a surrogate for hydrogen for safety reasons, and helium release rates were adjusted to provide the same constant volume flow rate as that required to release 5 kg of hydrogen over a four hour period. Supporting measurements included temperature and wind conditions. Helium was released upwards either as momentum- or buoyancy-dominated flows. Experiments were performed with the garage empty or with one of two conventional mid-sized automobiles parked over the release location. Six tests with the garage naturally ventilated and six tests employing forced ventilation with a fan are described. A variety of parameters were used to characterize the mixing behavior. Conclusions emphasized include the role of Froude number on helium mixing behavior, the development upper and lower helium concentration layers in the garage during a release, the measureable but limited effects of atmospheric wind on the results, the relatively efficient transfer of helium from the garage into the house during the releases, the ability of a vehicle to trap a high helium concentration in the engine compartment and, particularly, the undercarriage during a helium release and the relatively rapid drop in these levels to those of the surrounding garage at the end of the release, the relatively slow buildup of helium in the passenger compartment and trunk of a vehicle during a helium release and subsequent slow decay following cessation of the flow, the effectiveness of active ventilation in reducing helium concentrations in the garage to levels below those corresponding to flammable concentrations of hydrogen, and the trapping of helium/air mixtures c
Technical Note (NIST TN) - 1731
Report Number


attached residential garages, automobiles, buoyancy-dominated flow, forced ventilation, Froude number, helium concentration, hydrogen concentration, momentum-dominated flow, natural ventilation, wind effects


Pitts, W. , Yang, J. , Fernandez, M. and Prasad, K. (2012), Helium Dispersion in an Attached Single-Car Residential Garage with and Without Vehicle, Technical Note (NIST TN), National Institute of Standards and Technology, Gaithersburg, MD, [online], (Accessed March 4, 2024)
Created October 2, 2012, Updated November 10, 2018