a scavenging medical hood includes a hood for fitting over the head of a patient . a gas inlet port leads to the interior of the hood for supplying the interior of the hood with an appropriate respiratory gas and an aerosolized medicinal agent contained within that respiratory gas . a gas outlet connects between the interior of the hood and the ambient air for discharge of gas from the interior of the hood including any residual aerosolized medicinal agent remaining in that discharged gas . a vacuum port is located adjacent to the gas outlet . a vacuum is applied to the vacuum port via a suitable motorized vacuum source . vacuum at the vacuum port aspirates gas from the area of the gas outlet to aspirate respiratory gas , residual aerosolized medicinal agent still suspended in the respiratory gas and ambient air from the vicinity of the gas outlet into the vacuum port . a filter located in the vacuum line serves to filter out the residual aerosolized medicinal agent from the aspirate in the gas line .