When using a centrifuge, what should you always do before starting it?

The correct action to take before starting a centrifuge is to close the lid. This step is crucial for both safety and the proper functioning of the centrifuge. If the lid is not securely closed, it can pose a risk of injury to the user and damage to the equipment because of the high-speed rotation involved in the centrifugation process. An open lid can lead to spills or even the projectile ejection of tubes, which can be dangerous.

While placing the centrifuge on a stable surface, checking the sample weight, and securing the power source are all important considerations in ensuring the equipment operates correctly and safely, they do not take precedence over the need to close the lid. Closing the lid ensures that the samples are contained and reduces the risk of accidents once the centrifuge is powered on.