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The Frustrating Filter Fix
The Frustrating Filter Fix
A color film production facility was having a serious quality control problem and the building air filters were at the top of the suspect list.
Mysteries of Science

Dr. Gilleo
Mysteries of Science by Dr. Ken Gilleo
Dr. Gilleo is a chemist, inventor and general problem solver. Ken has been tracking industrial forensics and collecting case histories for decades. These cases are taken from the vast world of industry and commercial enterprise.

Check out Dr. Gilleo's eBook, 100 Mysteries Solved by Science. We hope you enjoy these case histories. You need not be an engineer or scientist to understand the problems and appreciate the solutions.
Transcript
This case takes place in a photographic film production facility in upstate New York. Color films are complex structures made by applying very thin coatings of dyes and other chemicals to plastic film under highly controlled conditions.

But the factory was having a serious quality control problem. The color intensity of the finish film was below specification on most of the runs.

The plant used purified air that was processed through HEPA filters and the filters were now the top of the suspect list.

Here's a clue. The filter units had a blue - purple glow emanating from the edges of the housing. The light was from a UV germicidal lamp inside.

So what's going on here?

Here's the rest of the story.

The only equipment change that happened during this period was the installation of air purifiers. Further inquiries showed that the purchasing department found a bargain on a quantity of filter units that included a germicidal UV lamp.

The UV germicidal lamp generated ozone by energizing oxygen. The ozone is a reactive gaseous molecule that is known for its oxidative and bleaching qualities. It kills germs, but can also bleach dyes.

The ozone was weakening the blue dye during the mixing process. The dye passed the initial QC inspection, but was degraded after many hours of exposure during mixing.
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