Loadings induced by deploying currently representative air bags were studied with driver surrogates (anesthetized swine) leaning against the system during inflation. Torso injury mechanisms were studied in a physiologic model, supported against a static steering wheel-mounted air bag system. Severe and extensive chest and abdominal injuries to the swine were observed in the tests. Loading caused by air bag deployment can occur in either of two phases. The first phase represents the initial punch out of the bag from the module; the second phase represents the membrane force of the inflating bag. Statistical analysis indicated that punch out induced injury because of the high rate of loading to the surrogate body region in direct contact with the air bag module. Membrane forces induced injury by high compression over a larger area. Punch-out loading might be reduced by allowing the bag to escape from other parts of the container not in contact with the driver during deployment. Loading by the inflating bag might be reduced by using a compliant steering system to support the module. The amount and rate of generated gas had only marginal effect on the cumulative injury. Even an inflator with inadequate gas output to protect a properly seated occupant had sufficient energy to induce severe injuries in a surrogate in contact with the inflating module. Analysis of the field relevance of the results must consider not only the injury potential given that a driver is in direct contact with the air bag module at the time of deployment, but also the expected field frequency of such an event. Analysis of the field relevance of the results must also consider the correlation of the laboratory test environment with real-world exposure.