25 October 2004
Fans. See paragraph 2-4.2. Use centrifugal fans with backward curved
blades, whenever possible. Centrifugal fans with radial blades are less efficient, but still
acceptable. Place the exhaust fan and the outlet ductwork outside of the building.
Weather Stack Design and Location. See paragraph 2-4.3 for design
Replacement Air Ventilation Systems. See paragraph 2-4.5. Design
dedicated mechanically supplied replacement air systems to maintain room static
pressures (relative to the atmosphere) ranging from -4.98 to -14.9 Pa (-0.02 to -0.06 in
Blast booths often do not have mechanical replacement air. In this case,
there is no control over the room static pressure for non-mechanical replacement air
systems. The extra negative pressure reduces exhaust fan performance. If
mechanically supplied replacement air is not feasible, ensure that the room static
pressure and the resistance through filters and louvers are included when sizing the
Heating and Air Conditioning
. See paragraph 2-6.2
System Controls. Design system controls in accordance with paragraph
2-5 and the following.
a. Install static pressure sensors at locations that represent the average
static pressure in each blasting room. This will enhance monitoring and
maintenance of desired blasting room pressures.
b. Interlock the blasting tool power supply with the ventilation system's
on-off switch. This will prevent the use of blasting tools without ventilation
SAFETY AND HEALTH CONSIDERATIONS. See paragraph 2-7, 29
CFR1910.94(a)(5), and ANSI Z9.4, section 7, for general requirements. Consider the
Respiratory Protection. Follow the guidelines in 29 CFR 1910.94(a)(5)
for respiratory protection requirements. The operator must wear a continuous-flow, air-
line respirator that covers the head, neck, and shoulders. Consider providing each
respirator hood with an adjustable, vortex-type climate control system.
Air Supply and Air Compressors
. For large booths, consider providing
multiple air hose connection points along the perimeter of the enclosure to
accommodate work in various parts of the booth.
Noise. See paragraph 2-7.2. Carefully select the blast nozzle. Nozzle
noise generation depends greatly on the discharge velocity. Consider using sound
barriers or dampening materials on enclosure walls. Protect the dampening material