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MANIFOLDING SPRAY BOOTH DUCTWORK AND IMPROPER AIRFLOW

Spray booth exhaust ductwork

In this photo, an installer has chosen to manifold three spray booth exhaust duct runs. (A manifold is a pipe or chamber branching into several openings.)

This layout probably looked great on paper and reduced the number of roof penetrations from three to just one.

Reality is such as nasty teacher.   The static pressure (resistance to the flow of air) was greater in the top portion of the ductwork than in the spray booths.  The ductwork downstream from the manifold point (above the joints) should be much larger than what is in the photo.   The air ventilated out of one booth actually flows into its neighbor.

Our booths are designed to meet specific airflow needs and we design them with ductwork. The spray booths in the photo were designed to have individual exhaust ductwork runs; they were not installed according to the design or instructions provided by Standard Tools.

Manifolding of exhaust ductwork is allowed by NFPA-33 only if devices exist in the ductwork that detect improper airflow.  The static pressure within the spray booth will change as the overspray builds up in the exhaust filters and as the obstruction within the booth changes (based on size and shape of parts in the spray booth).  This can be very technical and overly-complex.  The simple rule, and what Standard Tools recommends, is no manifolding of exhaust ductwork.  Keeping ductwork simple is the least expensive and best performing strategy in the long run. We suggest that you install your booth, and your ductwork, according to our recommendations to ensure proper airflow within your booth.

WHY DO I HAVE TO COMPLY WITH SAFETY CODES?

If you are reading this posting we can assume that you are smarter than the average person.  You have shown an interest in using and maintaining your paint booth and equipment in a safe and effective manner.  What happens when we neglect safe practices and don’t follow safety codes?

The Great Molasses Flood
Great Molasses Flood

In January of 1919, a molasses storage tank in a Boston neighborhood collapsed sending two million gallons of thick goo in waves through the streets, killing 21 people and injuring over 150 people. It’s known as the “Great Molasses Flood”. The city had deemed the structure unsafe for the weight of the material stored but had not enforced its findings.

 

Cocoanut Grove Night Club after the fire
Cocoanut Grove Night Club

On November 28th 1942, a huge fire occurred at the Cocoanut Grove Night Club in Boston. 492 people perished in total. The Cocoanut Grove was originally a speakeasy—an illegal bar during alcohol Prohibition—and some of its doors were bricked up or bolted shut. During the 1990s, former Boston Fire Fighter and researcher Charles Kenney had discovered and concluded that the presence of a highly flammable gas propellant in the refrigeration systems—methyl chloride—greatly contributed to the flashover and quick spread of the fire (there was a shortage of freon in 1942 due to the war effort). As a result of the Cocoanut Grove fire and tragedy, the fire ordinances were expanded.

Continue reading WHY DO I HAVE TO COMPLY WITH SAFETY CODES?

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