What should you do before entering an area where inhalation poisoning has occurred?

Before entering an area where inhalation poisoning has occurred, the most important action is to ensure your safety from potential exposure to hazardous substances. Taking a deep breath of fresh air, as indicated in the provided answer, implies that one is trying to prepare for an entry into a dangerous environment. However, this doesn't effectively safeguard against inhalation hazards.

The recommended best practice is to call for medical help and ensure that professionals assess the situation and manage the response. It may also be vital to wear appropriate personal protective equipment, such as a mask, to prevent inhaling toxic substances. Checking for breathing could be relevant after assessing the safety of the environment, particularly for any victims present, but it shouldn't be the first action taken in a potentially dangerous area. Always prioritize personal safety and ensure proper measures are followed before attempting to enter hazardous environments.