Each space is a filter plenum that measures approximately 40 x 40 x 20 feet. The only means of entry or exit is the submarine style door that is an airlock. It allows upright entry, but requires 15-20 pounds of pressure to open because of the negative pressure in the space. There is a 6 inch high door ledge that one must step over, which helps make the seal. When closed, it is air-tight and virtually sound proof.
Workers enter the space to change out filters or take readings.
Workers are required to wear PPE, including respirators, inside this space because the filters contain alpha emitters. An employee must enter to undo the bolts. Air monitoring is performed and no air quality problems have been detected. A permit program is in place and the response team is notified prior to each entry. The caller asked if DOE had issued any guidance on the confined space standard.