Film-Tech Forum ARCHIVE: Xenon exhaust cooling air

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Posted by Antonio Marcheselli (Member # 373) on 12-10-2001, 02:58 PM:

Someone told me that exhaust air coming from a projector with a xenon lamp is dangerous.
Is is true?

Bye
Antonio

Posted by Gordon McLeod (Member # 33) on 12-10-2001, 03:05 PM:

It may contain Ozone not from the lamp itself but from the ignition pulse
Almost all manufacturers of Xenon lamps are ozone free now

Posted by Antonio Marcheselli (Member # 373) on 12-10-2001, 03:09 PM:

Gordon,

For cooling needs I put the exhaust pipe of the projector in the hall of my theater. Do you think that it could be dangerous after long period of time?

Bye
Antonio

Posted by John Pytlak (Member # 331) on 12-10-2001, 03:28 PM:

If you smell the pungent odor of ozone, you should definitely vent to the outside. Some building codes may mandate it!

Even if the ozone levels are very low, some people are very sensitive to the smell, which may cause headaches, itching red eyes, or nausea in some individuals.

AFAIK, limits for ozone exposure are 0.1 parts per million TLV-TWA.

Here are some links:
http://www.inusacorp.com/applications.cfm#
http://www.osha-slc.gov/dts/chemicalsampling/data/CH_259300.html

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

Posted by Mark Gulbrandsen (Member # 72) on 12-10-2001, 03:52 PM:

Although all lamps now are claimed to be ozone free, there is no lamp can be 100% totally ozone free. The best thing to do is check about the loal codes in your area and see what is mandated for lamphouse exhaust. Some codes allow you to exhaust it into the ceiling, or open building area, and some mandate that it has to be let outside.
Mark @ GTS

Posted by Bernard Tonks (Member # 809) on 12-10-2001, 04:15 PM:

I have no flues to the outside from my xenon lamps, but I do have a fairly large and high ceiling projection box which is well ventilated. I or the other part-time projectionists have never experienced any ill or side effects. I have been told that a little ozone can be good for you, but I would think that can only be the seaweed variety.

As I mentioned in another thread my first experience with xenon lamps some 30 years on a days relief at the Classic Kilburn was with the first three electrode type which were not ozone free and the smell was putrid, and I did suffer from severe headache believe you me.

Posted by Andy Muirhead (Member # 712) on 12-10-2001, 07:12 PM:

I would be interested in hearing of any problems health wise in the emission of ozone from bulbs, as all four of our projection rooms have no external lamphouse extraction, i.e the extract from the lamphouse 'extracts' to the projection room - no feed to outside.

By the way Bernard, in profile, at least, you look like a double for Ian Hart (in your film-tech pic anyway)! Perhaps when your place closes for good you may get some work as a stunt double!

Posted by Gordon McLeod (Member # 33) on 12-10-2001, 07:14 PM:

If you read the name plate (boiler plate) on the back of many lamphouses it says "approved for indoor use when vented to the outside atsmophere"
I had to applie for a permit for the IMAX lamp to vent its ozone to the outside under canadian epa regulations

Posted by Bernard Tonks (Member # 809) on 12-11-2001, 08:09 AM:

Great idea Andy, perhaps you should start a thread for 'lookalikes' on Film-Tech! Though Joe Redifer could give you a problem, the man of many faces.

Posted by John Pytlak (Member # 331) on 12-11-2001, 12:55 PM:

Another disadvantage of venting directly to the projection room is that you are adding to the heat load. Most of the energy consumed by a xenon lamp ends up as HEAT, and kilowatts add up quickly in a multiplex. The heat usually causes a significant decrease in the relative humidity, which will aggravate static problems and film curl.

Posted by Antonio Marcheselli (Member # 373) on 12-11-2001, 02:39 PM:

Thsnks for your suggestions.
In effect the pipe is throw the air in the hall just for an experiment (I found that the projector now is very, VERY, cooler than usual), we will add a pipe to have the pipe itself pull out the air outside (in front of the main theater's door however...)

Bye
Antonio

Posted by Brian Vita (Member # 399) on 12-26-2001, 08:17 AM:

I've never seen a building code that specifically allowed you to dump exhaust air into the ceiling. Codes either specifically say that lamphouse exhaust must be exhausted from the building or they do not address it at all.

The ceiling dump method, while of questionable merits, is usually allowed by omission or by the ignorance of the inspector (ie. it goes through the ceiling therefore it must go out logic).

It is my understanding that ozone poisoning is somewhat like carbon monoxide poisoning in its symptoms. You sometimes get drowsy, light headed or head achey.

Many years ago a good friend of mine had a heart attack in a xenon booth. I noticed when I worked that booth I frequently got very drowsy. I often wondered.

------------------
Cinema Service & Supply, Inc. has a full line of new and used cinema equipment. We provide service throughout North America.
Brian Vita, President
Cinema Service & Supply, Inc.
75 Walnut St., Peabody, MA 01960-5626 USA
(800)231-8849/Fax(800)329-2775
+1-978-538-7575/Fax +1-978-538-7550
sales@cssinc.com /www.cssinc.com

Posted by Jerry Chase (Member # 660) on 12-26-2001, 11:42 AM:

"Another disadvantage of venting directly to the projection room is that you are adding to the heat load. Most of the energy consumed by a xenon lamp ends up as HEAT, and kilowatts add up quickly in a multiplex. The heat usually causes a significant decrease in the relative humidity, which will aggravate static problems and film curl."

While factually correct, I'm fairly sure this is incorrect in the inferred conclusion (That vented booths will have higher RH than unvented booths). Venting heated air into the same room will not adversely affect actual humidity. The same air (and moisture) are recycled. Moisture doesn't disappear, it only moves or changes state. As the temperature increases, there is a small decrease in the _actual_ humidity. This decrease is in direct relation to the expansion of the air, which will force a small amount of the air out of the booth.

Example: Given a volume of ten thousand cubic feet of air, a temperature rise from 70 degrees to 80 degrees F will expand to 10K(460+80)/(460+70), or 10,189 ft^3. Therefore, since a booth can't expand, 189 ft^3 of air flows out during the time of the temperature rise. This is a relatively insignificant amount of air and moisture loss.

The relative humidity DOES drop, since hot air is capable of "holding" much more moisture than cold air. About five quarts of water are in this same volume of air at 50% RH at 70 degrees. More moisture can easily be added to the booth by ducting this exhaust air from each lamp into the intake of a room humidifier. Since humidification requires energy to convert liquid water into vapor, it cools the air. This has the added benefit of slowing the booth temperature rise while increasing relative humidity. In addition, any stray ozone will become entrapped in the moisture pad and serve to sanitize the water in the humidifier.

Constantly venting the booth is much more of a problematic, since large volumes of air are extracted and the heat (and moisture) in that air is lost to the theatre (look at the CFM rating of any xenon lamphouse fan, and multiply that by the number of lamphouses to see the seriousness of the issue). That air has to be replaced by air from the general building or HVAC, and ultimately, the cold exterior air. During winter operation, this heated air can be incredibly dry. The air coming in from outside, if it is at 32 degrees F, is only capable of "holding" a little more than a quart of water in the same 10K ^ft., and usually holds much less water than that. Literally, to maintain a 50% RH in our hypothetical booth with one complete change of air, the energy required to boil at least a gallon of water into vapor has to be added to the energy required to heat the air from 0 degrees to 70 degrees.

In cold climates, the heating requirements and codes dictate a certain amount of fresh air exchange per person, based upon a full auditorium load, and the incoming booth replacement air effectively has no RH when heated. I have yet to see a theatre that properly maintains a 50% RH under these conditions. Unless air coming into the booth to make-up for the exhaust air is specifically humidified in the duct, and the booth held at a slight positive pressure, the booth suffers from low humidity as well.

In summary, I think that humidity problems in the booth are much better addressed during winter operation by primarily venting the lamphouse into booth humidifiers, reducing the overall energy requirements of the building. During summer operation, most of these vents can be switched to outside exhaust to reduce excessive heat and humidity buildup. Use of a "T" or "Y" connection and (motorized or manual) dampers could make this a simple operation that allows much more control over the booth "climate." If this system were coupled to an energy management computer, the entire booth could easily be maintained at 50% RH most of the time while substantially reducing heating costs, by minimizing the loss of heated moisture laden air to the exterior.

Posted by John Pytlak (Member # 331) on 12-27-2001, 01:54 PM:

Jerry: I appreciate the concern for energy efficiency and the desire to use the heat of the lamps to help heat the theatre in the winter. Does anyone make a heat exchanger that could capture the heat, but not risk having excess ozone in occupied areas? How about using outside air for lamphouse cooling? Both would make maintaining the recommended relative humidity of 50-60 percent RH easier to achieve.

When it comes to static and film curl, RELATIVE HUMIDITY is the determining factor. Heating the air LOWERS the relative humidity unless moisture is added with a humidifier.

Posted by Jerry Chase (Member # 660) on 12-27-2001, 03:13 PM:

The problem with many heat exchangers is that the humidity is not maintained. Air flowing in is warmed by air flowing out, allowing a 50% efficiency gain in totally dry air, but since the exiting moist air contains more energy than the dry income air, this efficiency is never attained.

There are recovery wheels Link that retain most of the moisture. Ozone can be removed through use of catalysts or activated charcoal filters. Again, air going through a humidifier pad would lose substantial amounts of ozone to the water.

Trying to duct incoming air to the lamphouse can be like herding cats; many lamphouses have multiple incoming air paths and require specific flow patterns.

Lamphouse exhaust considerations should, IMO, be re-evaluated now that carbon arcs are rarely used and bulb manaufacturers are reducing the amount of ozone generated, as Gordon mentioned.

Posted by John Pytlak (Member # 331) on 12-27-2001, 03:30 PM:

Thanks Jerry. Your suggestions are good. Ideal humidity is 50-60 percent RH. Ozone must be kept within EPA/OSHA guidelines.

Posted by Rory Burke (Member # 512) on 12-27-2001, 10:23 PM:

Honestly i dont think the ozone levels involved compare to those found east of Los Angeles in the Inland Empire. There are month periods where the ozone is so bad that there is less than 3 miles of visibility. Aircraft are put on mandatory instrument flight rules its soo bad. The inversion layer caused by the rapid heating and cooling of this desert areas air temperature prevent ozone and other gases from excaping into the air. I dont think any Ozone in any projection booth would even reach this high levels of contamination and thus cause any related health risks.. although there are more cases of allergies and pulmonary ailments reported in the Inland Empire as compared to the entire southern california region

Hope this puts projectionists at ease
Id worry more about getting jewlery caught in the sprockets or having a bulb blowing up before any ozone contamination.

Rory