Which of the following is NOT a method to control molecular contaminants?

Mechanical filtration is indeed a common method used in air quality management, but it specifically addresses particulate matter rather than molecular contaminants. Molecular contaminants, such as gases and vapors, require different control strategies.

Source control involves eliminating or reducing the sources of contaminants, which is effective in addressing molecular contamination at its origin. Ventilation or dilution helps by increasing the airflow in a space, thereby lowering the concentration of molecular contaminants in the air. Removal control, though less commonly referenced, can involve techniques that target the removal of specific contaminants from the air.

In essence, while mechanical filtration is an important aspect of air quality management, it primarily targets larger particles and does not effectively control molecular contaminants, which is why it is identified as the method that does not apply in this context.