The widely used method of synthesizing HCl and DCl gases for infrared analysis by hydrolysis of benzoyl chloride includes a potentially dangerous final step whereby the frozen product is allowed to heat and expand into an infrared gas cell. The subsequent rapid rise in vapor pressure can "pop" open glass joints in the vacuum line and vent the sample in the face of the user. We describe an improvement on this procedure whereby the product is collected at atmospheric pressure in a large flask, which can subsequently be transferred to the vacuum line for expansion into the infrared gas cell under negative pressure. The alteration described herein is applicable to essentially any synthetic method of HCl and DCl gas or other hazardous gases of spectroscopic interest.