Confined Spaces 25 determining if acceptable conditions exist in a permit space prior to entry, for authorizing entry with a permit, overseeing operations, and terminating the entry at the completion of work. Flammable Atmosphere An atmosphere that poses a hazard because flammable or explosive gases, vapors or dusts are present at a concentration greater than ten percent of their lower flammable limit. Hazardous Atmosphere An atmosphere which exposes personnel to the risks of death, incapacitation, injury, or acute illness from one or more of the following causes: • flammable atmosphere • airborne combustible dust • an atmosphere containing oxygen levels below 19.5% or above 23.5% • an atmosphere where the permissible exposure limit for a certain chemical has been exceeded and could result in exposure • any other atmospheric condition that is immediately dangerous to life and health Hot Work Any work that introduces an ignition source into a work area (welding, cutting, brazing, or soldering) . Hot Work Permit Guidelines Hydrogen Sulfide A toxic colorless gas that, at low levels, has the odor of rotten eggs. It is a chemical asphyxiant and its smell cannot be relied upon for adequate warning. Immediately Dangerous to Life and Health (IDLH) Any condition that poses an immediate or delayed threat to life or that would cause irreversible adverse health effects or would interfere with Authorized Entrants abilities to evacuate the permit space unaided. Lockout/Tagout The control of all hazardous energies within a system prior to performing service on the system. The Iowa State University Lockout/Tagout Manual w ill assist in complying with OSHA, Control of Hazardous Energies (Lockout/Tagout) Standard (29 CFR 1910.147). Non-Permit Required Confined Space A confined space NOT containing ANY of the characteristics listed under permit-required confined spaces may be considered a non-permit confined space. Oxygen-Deficient Atmosphere An atmosphere containing less than 19.5% oxygen by volume. Insufficient oxygen is available to sustain life. Oxygen-Enriched Atmosphere An atmosphere containing more than 23.5%oxygen by volume, which increases the potential for explosion or ignition of an explosive or flammable substance.