Direct thermal detection of the passenger is considered for use in a system that would suppress deployment of the passenger-side airbag for a rear-facing infant seat. The temperature at the surface of the front passenger's seat is compared with the temperature at the surface of the driver's seat. If the two temperatures differ by more than a preset amount the airbag would be suppressed. It is shown that when the ambient temperature equals the passenger's skin temperature (at about 35 °C) seat surface temperature does not distinguish a normally seated adult from a rear facing infant seat. Attempts to circumvent this problem by adding a heater were either too slow or too insensitive for an airbag suppression system. However, direct thermal detection may add reliability to some other type of airbag suppression system, such as one based on passenger weight.