Which of the following systems is prohibited from being located in an outdoor enclosure?

The correct response is that instrument air sources are prohibited from being located in an outdoor enclosure due to concerns regarding contamination and environmental influences. Instrument air sources typically require a controlled environment to maintain the integrity and quality of the compressed air used in medical settings. Exposure to outdoor elements can introduce moisture, contaminants such as dust and pollen, and temperature fluctuations that may adversely affect the performance and reliability of the air supply system.

In contrast, oxygen supply systems, vacuum systems, and medical gas cylinder storage can be managed effectively in outdoor settings with appropriate safety measures and enclosures designed to protect them from environmental factors. These systems can typically handle greater exposure to outdoor conditions, provided that they are properly secured, ventilated, and maintained according to safety standards.