Great job/post Bob, thanks!!!Media Filters
I have been reading and commenting recently about shop air filtration and the concern for it. My decision to write this was to give the LJ's community some facts about air filtration. Let me start with my knowledge base. I started my own air filtration business after my son was diagnosed with severe asthma at the age of 18 months. He is now 20 years old. My wife (an RN) and I immersed our selves into learning as mush as we could to make his breathing easier. We attended numerous seminars by some of the country's leading Dr's and filtration experts. After years of research we decided to open our own air filtration company mainly to provide people with similar problems a product that will work. As I was already a firefighter this was a second job. After receiving a career ending injury I was forced to retire from both the FDNY and my air filtration company. So now you have a little back ground on me, please let me give you some basic facts about air filtration.
I hear that some of you make your own filters from box fans, and that may work for a short time but think of the long term. What is the efficiency of that filter if you were able to test it and at what size particle? How is the filter attached to the frame of the fan? That doesn't sound efficient to me. First let me tell you that the most respirable particles are below 2 microns and most are below 1 micron. That means that when you inhale you breath in most particles of various sizes and exhale most of them even though you don't see them. The ones that are inhaled but don get exhaled are the particles in the range of 1 micron or less. That means they stay in your lungs and sinuses. Over time that builds up. It doesn't mean that we all will get sick but, we should think about how much we invest in our tools and consider an air filter as one of the most important tools in the shop.
There are many types of filters out there. I am going to speak about mechanical filters such as pleated media. That includes HEPA and HEPA like or type.
In order to be a true HEPA filter it must meet or exceed a DOP rating of 99.97% @ 0.3 microns. Be wary of filters that don't tell you the percentage and at what particle size. The DOP rating is higher than the MERV rating you may see on the filters at the box stores. Below is a chart to compare some filters.
Various Air Filters to MERV Ratings
- Throw-Away Fiberglass Media MERV 1 -MERV 4
- Pleated Media Air Filters 30% ASHRAE MERV 10 - MERV 11
- Pleated Media Air Filters 65% ASHRAE MERV 13
( 65% ASHRAE is about 20% effective on less than 1 micron particles)
- Pleated Media Air Filters 95% ASHRAE MERV 14
- True HEPA 99.97% @ 0.3 microns exceed the MERV rating
The reason some filters are called HEPA like or type is that they are also a pleated media. But are not tested and do not receive the DOP rating of a true HEPA.
One important concern with all filters is how does it seal in the frame. If is does not have a good gasket or seal then it doesn't matter how good the filter is because contaminated air will bypass the filter.
This is a short list of particles and the sizes:
animal dander approx. 0.5 - 10.0 microns
lead pain dust approx. 0.3 - 2.0 microns
wood & tobacco smoke approx. 0.01 - 5.0 microns
These are just some samples of particles and their sizes. Although some do go past even the HEPA rating the HEPA does remove some of the smaller percentage of the smaller particles.
When choosing a filter of any type remember that the more air changes per hour the more you will filter. One question to ask: Is the cfm of the unit rated before the filters are installed or after? If they can't tell you then you must assume that is is rated after. That will effect the cfm of the unit dramatically if it is rated before and puts a strain on the motor.
There is a lot more I can go into but I'm just trying to give some basics. As you can tell I am not a writer, but, in a future post I will go into some ERV.'s (Energy Recovery Ventilators) and carbon filters. I hope I haven't confused too many but the concern for our health should not be forgotten or over looked. I understand that cost is a factor but what is the cost of getting sick. I have included the website of the supplier that I used to use and you can get some more info there. I want you all to know I get nothing in return. I just believe in protecting your lungs. Feel free to contact me.
Thanks for reading my post.
All woodworkers should take heed to Bob's advice here.
If not you may end up with COPD (Chronic Obstructive Pulmonary Disease) as outlined in my blog: http://lumberjocks.com/topics/5872