Canadian Entry To Practice (CETP) Practice Test

The option indicating the addition of more odorant regularly is considered the correct answer because while this may be a common practice to maintain odor levels, it does not inherently serve as a prevention method against odorant fade. The term "odorant fade" refers to the diminishing presence or effectiveness of the odorant used to detect gas leaks.

Preventing odorant fade involves keeping the odorant sufficiently concentrated and effectively distributed in the gas mixture. Purging air from systems helps remove any odors that could interfere with detection, thereby ensuring that the remaining odorant is more effective. Pressurizing containers assists in maintaining the integrity and concentration of the odorant within the system. Closing the valve helps to prevent gas escape, which could otherwise lead to a loss of odorant.

Thus, while adding more odorant can help maintain scent levels after some has dissipated, it is not a direct method to prevent fade itself. The other methods listed directly relate to maintaining the conditions that help keep the odorant effective in the system.