What should be avoided when refilling SCBA cylinders?

Refilling SCBA cylinders with contaminated air is critical to avoid because doing so can compromise the air quality within the cylinder, potentially exposing the user to harmful contaminants when the SCBA is used. SCBA units are designed to provide clean, breathable air in hazardous environments, so using unclean or contaminated air directly undermines their purpose. Contaminants can lead to respiratory issues or other health problems for the user. Therefore, it's essential to ensure that only clean, breathable air is utilized during the refilling process to maintain safety and effectiveness.