## Core Concept
HEPA (High Efficiency Particulate Air) filters are designed to remove particles and contaminants from the air. They are commonly used in settings requiring high levels of air cleanliness, such as hospitals, laboratories, and cleanrooms. The core concept here involves understanding the application and effectiveness of HEPA filters in air purification.

## Why the Correct Answer is Right
HEPA filters are used to disinfect or more accurately, to remove particulate matter and microorganisms from the air. They have a high efficiency of capturing 99.97% of particles as small as 0.3 microns, which includes most bacteria, viruses, and fungi. This makes them particularly useful in environments where air needs to be free from airborne pathogens.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is incorrect because while HEPA filters do remove particles, the term "disinfect" specifically refers to the process of eliminating pathogens. HEPA filters do not actively disinfect through chemical means but rather through physical filtration.
- **Option B:** This option might seem plausible but is incorrect because HEPA filters are not primarily used for water purification. Water purification involves different technologies such as UV treatment, reverse osmosis, and filtration systems designed specifically for water.
- **Option C:** This option is incorrect because while surface cleaning is a method of disinfection, HEPA filters are used for air purification, not for cleaning surfaces.

## Clinical Pearl / High-Yield Fact
A key point to remember is that HEPA filters are crucial in infection control, particularly in areas like operating rooms, isolation rooms, and laboratories. They help prevent the spread of airborne pathogens, making them a vital component of hospital and laboratory safety protocols.

## Correct Answer Line
**Correct Answer: D.**