Which of the following describes a variation of the contamination control principle?

The concept of contamination control revolves around maintaining the purity of the air and preventing the ingress of pollutants or particulates that could compromise system performance or product quality. Cleaning the air required by the process directly aligns with this principle, as it involves removing particulates, allergens, or any potential contaminants from the air before it enters the system. This ensures that the air is free from particles that could affect operations, enhancing efficiency and safety.

The other options, while related to air quality, do not specifically describe a variation focused on the cleaning aspect in the same way. Adjusting air pressure may help in certain operational contexts, but it isn't directly a contamination control measure. Using chemical agents can help manage contaminants, but this approach does not necessarily clean the air in a traditional filtration sense. Implementing an ozone treatment system addresses air quality through oxidation, which may not be a direct cleaning method and can introduce additional concerns, such as safety for certain applications. Thus, cleaning air specifically addresses the core of contamination control effectively.