Any area considered to be a permit-required confined space must be posted at all entry points with a warning sign that reads:

The requirement to post a warning sign that reads "DANGER - PERMIT-REQUIRED CONFINED SPACE - DO NOT ENTER" is in line with OSHA regulations governing confined spaces. This type of signage is crucial for ensuring that individuals understand the specific risks associated with entering a confined space that requires a permit. The phrase "PERMIT-REQUIRED" informs workers that there are significant hazards present that necessitate adherence to specific safety protocols and procedures before entry can occur.

In this context, labeling the area clearly helps to prevent unauthorized access and ensures that everyone recognizes the potential dangers. This is essential for maintaining safety and health standards in the workplace, as it minimizes the risk of accidents or injuries among workers who may be tempted to enter without proper training or authorization. The explicit instruction "DO NOT ENTER" reinforces the message, making it clear that entry without proper safety measures is strictly prohibited.

Other options do not align with OSHA compliance and may not accurately convey the necessary level of seriousness regarding the hazards present in such spaces. Therefore, the selected answer effectively communicates the essential information needed to maintain a safe working environment around permit-required confined spaces.