Remember Only the naive assume conditions regarding a confined space. The only safe assumption about a confined space is that Murphy's law prevails. Workers should never assume that the space that has tested safe will remain safe. Nor should they assume the reliability or worthiness of their safety equipment. Workers who lack an understanding of their equipment's operation and effectiveness are gravely disadvantaged.
Confined spaces deserve respect.
Standard Operating Procedures for Working in Confined Spaces. Cover each step required to flush, ventilate, or otherwise ensure that all proper precautions have been taken for safe entry into, and for safe work in, the confined space. Identify all equipment and the methods used to test and monitor conditions before and during entry into and while working in the confined space. List the safety equipment required at the work site- and at the plant site, if needed. Identify the minimum safety equipment that each worker in the confined space and the top-side attendant must wear.