A gas cell containing SF6was irradiated with pulses of infrared radiation from a CO2laser. The time dependence of the transmittance of this cell is explained theoretically by means of a combination of saturation and heating. Heating effects are important even at SF6pressures below 130 Pa. Intermolecular transfer of vibrational energy must play a major role in delocalizing the heating at pressures below 110 Pa. The transmittance of SF6gas irradiated by a chopped CO2laser beam depends upon the width and spacing of slots in the chopper wheel and upon the rotational frequency of the wheel.