Film-Tech Forum ARCHIVE: Attack of the Dust Bunnies!

This is topic Attack of the Dust Bunnies! in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Randy Stankey (Member # 64) on 06-04-2000, 10:42 PM:

I guess this is mostly for other Cinemarkers because it's building-specific... but has anybody had this problem?

Our building has been said to be the last of the "Tinseltown" design. It was built in 1996, just before they switched to the "stadium" design. In fact, they say our building was almost going to be stadium until they changed their minds at the last minute... Anyway, here's the problem:

Every morning when you go in to open up you find all the platters and the tops of the lamphouses covered with dust bunnies. It seems that when the air conditioning kicks-on in the morning the "surge" of air blows all the crap out of the ducts and out into the room. Of course, somebody had the bright idea to put all the vents right above the projectors!

Sometimes it hapens during the day, too. Especially if it's hot outside and the AC cycles on and off a lot. (It only happens diring the summer when the AC runs -- Not when the burners run for heat.)

I'm not entirely sure which duct it's comming from. It might be the ventillation ducts or it might be the air-return ("balancer") ducts.

Of course, having dust bunnies attacking our film isn't a good thing. Especially since we've worked so hard in the last year to clean up our presentation. It feels like one step forward and two steps back, sometimes!

Any ideas?

Posted by Brad Miller (Member # 2) on 06-04-2000, 10:57 PM:

I know of one theater that went out and purchased cheap air filters and cut them to size to fit in the vents. Another option if the bunnies are large enough is to buy you some of that wire mesh material that is used on screen doors. Either can be done so that it is not visible when the cover is on.

Of course, every couple of months, someone is going to have to pull the cover off and dump the bunnies into the trash or you will soon find yourself working in a non-airconditioned booth.

Posted by Randy Stankey (Member # 64) on 06-04-2000, 11:33 PM:

They are pretty small. About 0.5 cm in diameter, or smaller. Sometimes it's just a blanket of fine, grey dust.

Do you mean to put the filters up, inside the diffuser or just attach it to the outside? The diffusers have fire traps inside them. -- They are two 1/2 circle flaps, hinged at the center. There's a fusible link holding them open and a spring to pull them shut. It'd be a bitch to put the filter inside. Not to mention the trouble pulling the grilles off and getting all filthy when the dust comes out!

Posted by Brad Miller (Member # 2) on 06-04-2000, 11:46 PM:

Sounds like in your case, you'll have to be satisfied with mounting the filters over the vents. It won't look pretty, but the customers don't come to see the booth's air vents.

Posted by Randy Stankey (Member # 64) on 06-04-2000, 11:55 PM:

I thought you might say that. The only other option would be to get up inside there and go to town on all the ducts with a duster and a shop vac. Not a pleasant job. Not to mention, there are noise baffles up inside the ducts too.

Maybe it would be better if we hired someone? (THAT will be the day!)

Posted by Bruce McGee (Member # 131) on 06-05-2000, 06:46 AM:

Hey Randy! This is a subject that I KNOW.

Has your theater got electronic air cleaners instead of regular air filters installed in the HVAC system?

When they are turned off, the minute particles that collect on the charged surfaces are released and in some systems the particles fall into the ducts. The next time the blower starts....

If no EAC system, how often are the air filters changed? I've seen many commercial set-ups that have had the same filters in them for months, and are clogged. Also, who supplies the filters? Your theatre or the service co? If you can see through the new filters, just think how much crud gets thru them. I look for filters that are thick. They cost more, but are worth it.

I have an EAC on my home HVAC system that had problems blowing white dust all over everything. I installed the filters just past the EAC and stopped all dust. All I have to do is vacuum the filter surface every couple of months and they last forever, well, a year or more anyway.

Honeywell Air Systems RULE!

(I do not work for Honeywell, but I DID work in heating and cooling for 7 years!)

Posted by John Pytlak (Member # 331) on 06-05-2000, 08:10 AM:

Really efficient disposable air filters (e.g. 3M "Filtrete") are readily available and relatively low in cost. Use the "HEPA" pleated media filters rather than the cheap spun fiberglass filters. The "HEPA" filters trap dust particles down to the sub-micron size. Good filtration of the incoming air will not only keep the film cleaner, but also electronic (disk drives) and optical components (reflectors, port glass). If necessary, you could make frames to hold standard-size filters in front of each air duct. Don't forget to change the filters when they load up with dust.

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com

Posted by John Walsh (Member # 168) on 06-05-2000, 09:34 AM:

Another cheap thing that might help is some kind of baffle to keep air from directly blowing on the platters; something to direct the airflow out to the middle of the room. The filter on the vents is a better idea, though.

I wish I had a nickle for evey stupid architect mistake, like vents directly over the film, or (my fav) return ducts behind the screen so dirt get drawn into the holes.

In "clean-rooms" for IC wafer maufacturing, they find that (after filtering the incomming air) the next problem is dust from people's clothing. The doors to clean-rooms have an "air-wash," where a big blower blasts you (while in a sort of air-lock) before you go in.

If an even "cleaner" room is needed, that's when they make you wear the "bunny-suits."

I actually wanted to make a simple version of a clean room at a 10-plex theater we were building a few years ago to use as a prototype to see if it was worth designing in all of our new theaters. I had read about clean-room design and wanted to take some of those ideas, (using a certain kind of paint and ceiling tiles, separate closed filtered intake for the lamps, etc.) but (no surprise) no one in management was interested.

Posted by John Pytlak (Member # 331) on 06-05-2000, 10:07 AM:

"Cleanrooms" magazine has much information on contamination control:
http://www.cleanrooms.com

Cleanroom technology is essential to the manufacture of microelectronic components and photographic film. Kodak's film and microelectronic manufacturing areas have air-jet/vacuum "people washers" and require "bunny suits" (cleanroom coveralls for shoes, clothing, hair and beards) to enter.

Such extreme measures are usually not needed for projection rooms. Easily cleaned worksurfaces, good air filtration and good housekeeping are usually all that is needed to maintain clean film images. On-line film cleaners are recommended to remove any dirt picked up during projection.

The most important "rule" is not to let the film or leader come in contact with a dirty surface. Operators who say "it's only leader" or "I don't have time to wipe off the rewind bench" are usually the ones with the dirty prints.

Posted by Randy Stankey (Member # 64) on 06-06-2000, 02:07 PM:

We have a service company that comes to change the filters in the HVAC every few months. They were in a couple of months ago. They use what Mr. P. said, "spun" filters. They look like polyester fiber "batting". They are blue on one side and white on the other. Sometimes I wonder about those guys. One time we'll get a really good guy and others we'll get a really goofy one. Last time they were in one of the intake dampers got busted. Seems that the filter got put in wrong and it wedged the control arm. When the motor tried to shut the damper, it couldn't and burned out. It all had to be replaced.

I'm not sure it's the intake filter. I just think the ducts are dirty. Since it only happens when the AC is on, maybe it's the condenser coil?

The HVAC units we have are Trane. We have Novar control system. All I can say is "Nothing runs like a Trane". -- "Clickety Clack! Clickety Clack!". As far as "Novar", take of the "r" and it's "No va" -- Spanish for "Doesn't Go."

I guess what I'm going to have to do is call the HVAC service guys and ask them. Next time I see the filter guy, I'll ask him too!

Posted by Bruce McGee (Member # 131) on 06-06-2000, 06:59 PM:

Maybe they are not changing the filters often enough? The Condenser is the part that is outside on the A/C system. The Evaporator is inside the duct work, unless this is a package unit on the roof. Most commercial systems that I installed used a low or medium speed on the motor for heating, and high for cooling. Maybe the system is running when they change filters? If so, they are stupid. All that does is get the evaporator coil dirty, reducing efficency, and spread junk thru the duct system, which is what you are probably seeing on the equipment. Spun filters are OK, but cheap filters are no bargain! I am using Precisionaire PSF filters in all the systems that I service. I've never had a dust problem with them. The company that I worked at for all those years has used them for 15 years. They come in all standard sizes.

You might check, if possible, to see if all the filters are installed correctly. There is an arrow pointing which way the air is supposed to flow through them. It does make a difference!

Trane stuff is good. GE made the compressor that they used to hawk as being indestructable (Remember the Weathertron® heat-pumps of the early '80's? Same compressor, and they are still running.)
Most heat-pumps last around 10-12 years before the compressor dies. GE no longer owns the compressor design, or has leased it to Trane and they now build it themselves.

I have installed several roof-top package systems over the years, but no theatre jobs. I always hoped that I could do that just once!

It would be a good idea to install filter material over the supply ducts in the booth. They can be changed every month or so when they get dirty. Unfortunately, the duct system is probably caked with grey dust by now. Changing to better filters will fix the problem, but, all the crud that is in the ductwork will have to work its way out.

Hope I have not bored you to death.
Bruce

Posted by John Walsh (Member # 168) on 06-07-2000, 01:14 PM:

JP wrote: "Such extreme measures are usually not needed for projection rooms."

Oh, yeah. I just meant I thought using a few simplified ideas might work. The three big things I wanted to do was; a tight seal around the port windows for noise and dirt; ceiling tiles that don't 'rain' little fibers down, and a filtered closed-loop for the lamphouses. So much air gets sucked in by the snood that the whole area there (the gate, trap, intermittent) gets pretty dirty. I wasn't thinking about 'sticky-floors', etc.

Hell, I'd be happy if some of these 'threader-uppers' would simply wipe their burger-juice off the rewind table when done!

Posted by Jason Burroughs (Member # 68) on 06-07-2000, 01:40 PM:

Cinemark has been using the Norvar/Trane package for some time, and in my experience they both work pretty well. Bruce was right about the compressors, I've never seen one of them having to be replaced, and they get quite a workout here in Texas, Weakest point I've seen in the Tranes (particularly the older models) is the condensor coils, they have some weak spots in the line and leaks will eventually develop allowing the Freon to leak out. Compare that to the Aaon's and Lennox units that I've worked with they're top notch. I think the key points have already been touched on, make sure the filters are replaced on a regular basis and done properly, seal the port windows as much as possible, you'll notice the port windows get DIRTIER on the outside than the inside due to the enviroment of people comming and going, draperies, chairs capret etc... One thing you might suggest, since you're theatre is a few years old is to have the ducts in the booth professionally cleaned.

Posted by John Pytlak (Member # 331) on 06-07-2000, 02:04 PM:

Jason:

I agree with your suggestion to have the ducts professionally cleaned if they have a buildup of debris. Even new ductwork often has alot of construction "crud" left in them. Once the ducts are cleaned, be meticulous in changing the filters properly and frequently.

Another worthwhile idea to improve booth cleanliness is to have a central vacuum cleaning system installed, exhausted to the outside. Using a shop vac, broom, or dry mop just tends to stir up the dirt, so it lands elsewhere. Wet-mopping works well if you're on a budget.

The guy who thought of using blowers to clean the auditorium should be made to clean out each perforation in the screen with a toothpick, one hole at a time! The dust raised by the blowers also finds it's way onto the port glass, and even into the booth. I recall another thread mentioned watching the placement of the HVAC ducts so they don't suck or blow dirty air through the perforated screen.