Ideal location for a hanging air clearner

[Shawn Russell]

My shop is roughly 10' x 16'. The ceiling height is 9'10". I have a soffit that runs both sides of the 16' wall. The depth of the soffit is 19". The width on of the soffit on the East wall is 36" and the width on the opposing wall is 24"

I have 6x 2'x4' lights that run in two rows perpendicular to the 16' wall.

My thoughts are to mount the air cleaner under the soffit on the East wall just above the double door.

Is this the ideal location for placing an air cleaner? Would I be better off to mount it closer to the ceiling in the center or towards the North/South wall? I am curious if my shop layout would create air pockets where air would not circulate effectively due to the change in elevations?

Shawn

[Ralph Boumenot]

When I put a air cleaner in my old shop it was recommended to put it in the center of an outside wall. Two air cleaners opposite each other would be ideal. It was so long ago that I don't remember where I got the info (on WWW for sure). I do recall that it had to do with setting up a circular air flow around the shop.

[Howard Acheson]

Here are some general rules based on Nagyszalanczy's "Workshop Dust Control" and some of my own experiences and thoughts.

The two most important criteria for an air cleaner are the CFM and the filters. You want a CFM factor that will clean the size of your shop and a filter that removes the particle size that you are concerned about.

To determine the size or required air flow, use this formula: Volume of your shop (Length x width x Height) times Number of air changes per hour (typically 6 - 8) divided by 60. This will give you an answer in Cubic Feet per Minute which is how air cleaners are measured. MOST AIR CLEANER MANUFACTURERS RATE THE CFM OF THE FAN ONLY, but there are losses due to the filters. If you are building your own or if the air cleaner you are purchasing rates only the fan, figure you will lose about 25 - 40% for filtering losses.

As important as the air cleaner size is how and where you mount it. Try to mount at about 8-10 feet above the floor (no lower than 6'or 2/3 of the floor to ceiling distance if less than 8' ceiling). Mount along the longest wall so the intake is approximately 1/3 the distance from the shorter wall. Mount no further than 4-6 inches from the wall.

The exhaust is the largest determiner of the circulation pattern. You are trying to encourage circulation parallel to the floor/ceiling so ceiling mounting is not recommended. Use a smoke stick (or a cigar) to observe and maximize circulation. Use a secondary fan to direct air to the intake if necessary. Also, consider that a standard 24" floor fan moves a lot of air and, in some shops, just positioning it in a doorway with a window or other door open can accomplish as much or more than an air cleaner. It's all in the circulation patterns.

The exhaust is the clean air so that is where you want to position yourself. Do not place the air cleaner over the a dust producer. That will guarantee that the operator will be in direct line between the dust producer and the air cleaner. The operator wants to be in the clean air stream. If the dust has to pass your nose to get to the air cleaner, you get no benefits. If you have an odd shaped shop, two smaller units may be better than one large one.

DO NOT RELY ON A AIR CLEANER TO ACT AS A DUST COLLECTOR. The purpose of and air cleaner is to keep airborne dust in suspension and reduce airborne dust as quickly as possible AFTER THE DUST PRODUCER HAS BEEN TURNED OFF.

Finally, if you are looking for health benefits, you will not find any air cleaner manufacturer that makes health claims because there are few health benefits. CATCHING DUST AT IT'S SOURCE IS THE BEST LONG TERM GOAL. Rick Peters', author of "Controlling Dust in the Workshop", makes the point that spending your money getting the dust at its source is a better investment than trying to capture it after it is already airborne. If the dust is in the air, it's going to be in your nose and lungs too. Robert Witter of Oneida Air Systems has noted that "overhead cleaners can only lower ambient dust levels AFTER THE SOURCE OF EMISSIONS IS SHUT DOWN, and they take several hours to do this. This is why they are not used in industry." The absolute best answer, if health is the primary concern, is to use a NIOSH approved respirator. The dust cleaner will help keep your shop cleaner but have minimal or no health benefits. OSHA takes this position too. They measure the number of particles per a volume and most air cleaners will not satisfy their specs.

[Larry Frank]

I think that it may be a stretch to suggest that air cleaners are not used in industry. Where I worked, they were used extensively and were very effective. But these were industrial units. One can run a search on industrial air cleaners and come up with a large number of hits and some of these are HEPA units.

I agree that the primary reduction of dust should be at the source. However, it is not possible to collect all of it. If the dust levels in my shop get too high, I will turn on the air cleaner and leave for 30-45 minutes and when I return, the dust levels are much lower. I have a difficult time coming to understand how this is not a health benefit.

I have also found that the use of a HEPA vacuum attached to such things as sanders and other things which produce fine dust are very effective.

My intent is to use every device that I can including an air cleaner to keep the dust to a minimum.

[Howard Acheson]

>>>> If the dust levels in my shop get too high, I will turn on the air cleaner and leave for 30-45 minutes and when I return, the dust levels are much lower.

Nothing wrong with your statement as far as it goes. However most woodworker are pursuing the grail of a dust free environment while they are working in their shop. An air cleaner is not going to do that. As I said in my response above, the air cleaner only begins to reduce the dust once the dust producer is turned off.

>>>> I have a difficult time coming to understand how this is not a health benefit.

Sure, anything you due to reduce your time in the dusty room is a benefit. But the question is whether what you are doing is truly reducing your chances of health issues.

[Larry Frank]

I would really like to get a references for the statements..

"The dust cleaner will help keep your shop cleaner but have minimal or no health benefits. OSHA takes this position too."

Perhaps, someone could point to references which provide some data to support this position. I would like to understand this subject better.