Caring for Medical Emergencies I From Brady's First Responder (8th Edition) Progress Indicator: Question 3 of 20 3.  How does the diffusion rate of gases vary? Choices: Their rates of diffusion vary in inverse proportion to the square roots of their densities.  (Light gases diffuse more rapidly than heavy gases). Light gases diffuse easier then heavy gases. Heavy gases diffuse more rapidly than light gases. None of the above.