It's definitely true that clothes can hold onto the gas.... In my air force days, we'd go thru chem training every year where they tear-gas us in the "confidence chamber". We'd stand around in the tear gas with our mask on, then one by one step to the door, remove the mask, take a breath and give our name/rank/serial number before they'd let us out. Right afterwards, we had someone in my barracks wash their uniform in hot water, and everyone on that floor was coughing and eyes watering.