When monitoring for confined space entries involving a descent into stratified atmospheres, how far should the atmospheric envelope be tested?

When conducting monitoring for confined space entries into environments with stratified atmospheres, the recommendation is to test the atmospheric envelope at a distance of 4 feet from the entry point. This particular distance is critical because it allows for accurate assessment of the air quality and potential hazards before entry.

In any confined space, the atmosphere may vary at different heights or levels due to factors like temperature gradients and the presence of hazardous gases or vapors. An envelope test at this specified distance helps ensure that any harmful conditions, such as insufficient oxygen levels or the presence of toxic gases, are identified prior to personnel entering the space.

Conducting atmospheric monitoring at 4 feet is sufficient to establish a reliable safety zone, giving occupational safety professionals the necessary data to determine if it is safe for workers to descend into the space. This protocol is aligned with safety standards and best practices in confined space entry procedures.