If supplied air is required for confined space entrants, be absolutely certain that the source of air meets breathing air standards. It is recommended that breathing air meet or exceed NPFA 1989; the standard for first responders and emergency services workers. If workers use supplied air, ensure that the source of air meets Class D breathing air requirements. Over the years, we have accessed breathing air sources and have encountered non-compliance far more often then one would hope to. Some notable non-compliances have been; use of incorrect compressor lubricant causing oil mist to become entrained in the supplied air; lack of or ineffective filters and filtering; lack of documented analysis of supplied air; compressor intake near the exhaust of internal combustion engine. When preparing to work in a confined space, follow all applicable rules and requirement and carefully assess the suitability of your procedures and equipment for confined space activities.