What should be checked first when donning SCBA?

When donning a Self-Contained Breathing Apparatus (SCBA), the first priority is to ensure that the fit around the face is secure and proper. A correct fit is crucial because it creates an effective seal that prevents contaminated air from entering the respiratory system. If the mask does not fit properly, it can lead to exposure to hazardous environments, compromising the user's safety.

Achieving a good fit also affects the comfort of the wearer, which is vital during prolonged use. A well-fitted facepiece allows for more effective communication and reduces the risk of physiological stress or panic that could occur if the mask is not secure or is uncomfortable.

Other factors such as the oxygen level in the tank are indeed important, but they can be verified after ensuring that the facepiece is fitted properly. The temperature gauge and visibility of the facepiece relate to functionality and comfort but checking the fit is essential as the primary step before proceeding to assess those aspects.