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ANSI Z9.4 sections 5.3 and 5.4. Position the observation window in the blast room
walls and door as necessary so workers inside the room can be seen from outside the
room at all times. Use several doors and windows in large rooms. Provide emergency
exits on opposing walls. Make personnel and equipment doors operable from both
inside and outside of the room.
Air Cleaning Devices. See paragraph 2-4.4. Design in accordance with
29 CFR 1910.94(a)(4)(iii) and ANSI Z9.4, section 6.3. Consider using a pulse-jet,
pleated paper cartridge type dust collector and the following.
a. Replaceable explosion vents on the collector hoppers in accordance
Platforms leading to all elevated access hatches.
Fan located on the clean side of the collector.
d. Place dust collectors outside of the building for all blasting
applications. NFPA 65 specifically requires that the air pollution
equipment be located outside when blasting on aluminum or aluminum
Recirculation. Do not recirculate exhaust air when operations generate
toxic materials. If exhaust air recirculation is permitted, design the system in
accordance with the ACGIH IV Manual, ANSI Z9.4 (section 6.3) and ANSI Z9.7, 29 CFR
1910.1025 (lead), and 29 CFR 1910.1027 (cadmium). The outdoor air volumetric
airflow rate must be sufficient to keep the contaminant below 25 percent of the MEC.
Media Reclamation. Design in accordance with 29 CFR 1910.94(a)(4)(ii)
and ANSI Z9.4, section 6.2. Do not integrate the exhaust ventilation system with the
media recovery system.
a. Protect the media recovery system and ductwork from moisture and
rainwater intrusion to keep the media from caking and plugging up the
b. Use mechanical recovery systems such as rotary screw conveyors for
heavy media (steel shot).
c. Consider using pneumatic recovery system instead of mechanical
recovery system for plastic media.
Ductwork. See paragraph 2-4.1. Do not use spiral lock seam duct. Size
the exhaust ductwork to maintain a minimum transport velocity of 17.8 m/s (3,500 fpm).
Specify flat backed elbows per the ACGIH IV Manual, Chapter 5, Figure 5-25.