Final answer:
The atmosphere of a permit-required space should be tested before and after entry to ensure safety.
Step-by-step explanation:
The correct answer is C. Before and after entry.
When entering a permit-required space, it is important to test the atmosphere both before and after entry to ensure the safety of the individuals entering. Testing the atmosphere before entry allows for the identification of any potential hazards or risks that may be present, while testing after entry helps to confirm that the atmosphere remains safe for continued work.
By conducting tests both before and after entry, you can effectively monitor and maintain a safe working environment in permit-required spaces.