Final answer:
To disinfect air, both ultraviolet light and HEPA filters can be used. Ultraviolet light damages the DNA of microbes, while HEPA filters physically capture them from the air. Ethylene oxide is not suitable for air disinfection in occupied environments.
Step-by-step explanation:
The substances that can be used to disinfect air include ultraviolet light and HEPA filters. Ultraviolet light is a form of nonionizing radiation that can effectively control microbial growth by causing damage to the DNA of microorganisms, primarily through the formation of thymine dimers. This form of disinfection does not penetrate cells or materials like plastic and glass, thus direct exposure to UV light is necessary. HEPA filters, on the other hand, physically remove microbes, endospores, and viruses as air flows through them and are commonly used in hospital ventilation systems and biological safety cabinets to prevent the spread of airborne microbes.
From the options provided, ethylene oxide is not typically used for air disinfection as it is a gaseous sterilant used for medical devices and cannot be safely used in environments where people are present. Hence, the correct answer to the question, which of the following can be used to disinfect air is D) both HEPA filters and ultraviolet light.