Which factor is NOT cited as affecting chemical permeation rates?

• A. Humidity
• B. Temperature
• C. Thickness
• D. Previous exposures

Answer: (A)

Humidity is not cited as affecting how fast chemicals permeate through protective barriers. The factors you typically see called out are temperature, barrier thickness, and prior exposures. Higher temperature increases molecular motion and diffusion, so the permeation rate goes up. A thicker barrier forces a longer diffusion path, which reduces the rate. If a material has been exposed previously, it can undergo changes like swelling, softening, or microstructural damage that alter how readily a chemical can pass through. While humidity can influence some specific materials in particular situations, it isn’t a general factor listed for permeation rate in standard practice, making it the one not cited among the common influences.