May 2, 1997

The Directorate of Technical Support received information regarding potential fire and explosion hazards in the workplace associated with improperly installed cyclone dust collectors in the woodworking industry.

The information provided to us indicates that in some facilities, cyclone dust collectors are installed inside buildings. In this regard, we reviewed the 1994 Uniform Building Code (UBC), the 1994 Uniform Mechanical Code (UMC) and the most recent National Fire Protection Association (NFPA) standard on the prevention of fires and explosions in wood processing and woodworking facilities. In addition, we contacted and interviewed code interpreters of the International Conference of Building Officials (ICBO), who publish the UBC and UMC regarding the interpretation of these codes.

The 1994 UBC is one of three national building codes and is used in 25 states, predominantly west of the Mississippi. Architects who design light industrial facilities such as woodworking shops would refer to Section 307.8 of the UBC titled special hazards in Group H facilities. This section contains the requirement to provide a dust-collection system with approved explosion venting or containment. No mention is made of where to locate the dust-collector.

The 1994 UMC is one of three national mechanical building codes and is also used in 25 states, predominantly west of the Mississippi. Mechanical designers for light industrial facilities such as woodworking shops would refer to Section 505 of the UMC titled Product-Conveying Systems. Section 505.1 requires that "dusts conveying explosives or flammable vapors, fumes, or dusts shall extend directly to the exterior of the building without entering other spaces." This wording is consistent with outdoor locations for dust collectors but does not make that distinction outright.

The 1994 UMC Application Interpretation Manual is a companion document to the UMC. Local permit-granting jurisdictions refer to the guidance of the non-mandatory Application/Interpretation manual to assist with interpretations. These jurisdictions, however, are ultimately responsible for making interpretations of the building codes. One of the interpretations offered for section 505 of the 1994 UMC states, "A typical system for a woodworking plant would be designed as a Class 2 duct system with centrifugal separation outside the building."

NFPA Standard 664 "Prevention of Fires and Explosions in Wood Processing and Woodworking Facilities" Chapter 8, Woodworking Dust-Control Systems, Section 2.2 states, "Dust collectors shall be located outside of buildings." Two exceptions are listed which permit dust collectors to be located inside of buildings:

1. If they are located adjacent to an exterior wall, or vented to the outside through straight ducts not exceeding 10 feet (3 meters) in length, and have explosion vents.
2. If protected by an explosion suppression system meeting the requirements of NFPA 69, Standard on Explosion Prevention System.

In summary, NFPA Standard 664 requires cyclone dust collectors be mounted outside of buildings. In addition, guidance documentation (the UBC and UMC Interpretation Manuals) specifies that cyclone duct collectors be installed outside. If dust collection cyclones are found installed inside woodworking facilities, compliance and consultation personnel should indicate that the aforementioned industry sources recommend that dust collectors be moved outside if NFPA exceptions are not being met.

Moreover, it should be noted that it is important that the manufacturer's installation instructions be followed and that all electrical components of the dust collector must be approved by a Nationally Recognized Testing Laboratory (NRTL) as required by OSHA standards.

Please distribute this bulletin to all Area Offices, State Plan States, and Consultation Project Offices, and to appropriate local labor and industrial associations. Copies of this HIB may be used for outreach purposes.