Outdoor Air Filtration

With so many wildfires, smoke filled skies have become an annual occurrence for much of the western US. So I am wondering if it would be worth while to set up some kind of outdoor air filtering or cleaning system every summer? When people talk about clean air, they talk about trees and planting trees. And trees do the important work, to be sure. Rain also washes smoke from the sky. But there are places where I do not want to plant trees and there are long stretches of summer that do not have rain. What other tools can I add to my toolbox to help clean the air around my house?

My first thought was to send two furnace filters aloft with a kite. Like the illustration below.

Then I thought about the open-air markets in places like Morocco and Arabia. They are known for all kinds of canopies and shade cloths. I wonder if those also have air filtration benefits? I have wanted to put up a shade cloth between my house and my garage. That area catches a lot of wind (we just put an umbrella style clothesline out there). What if I were to hang a big sheet or two vertically? Maybe it would catch some dust and smoke particles and make them fall to the ground? Maybe when I take them down at the end of summer they would smell really smoky?

The third idea would be to imitate patriotic bunting. I could take some air filter material, hang it from the eaves of the house, or between buildings, and tie it into fancy shapes. Air filter material is usually white, so it wouldn't look as festive as a red, white and blue rosette. But tulle is white and it looks pretty good when it it tied up.

Do you guys have any ideas for how we could clean the air around us?

Hello!

I work in paper-making but in reality it is in filtration media production including but not limited to making air filtration media.

Filtration media has many different materials used to make the 'web' that captures particulates from cellulose, glass fiber, and synthetics.

Increasing demand for performance, capacity, and now reduced energy input has been pushing filter media into some really incredible directions with both pros and cons coming from it. We are seeing less PFOAs and harmful chemicals going into the resin application process but now are seeing more synthetic raw material being incorporated. Depending on what filters you utilize could have any sort of multiple variations of pulp and resin to get the characteristics that the customer wants.  

Let me now dive a little bit more into your ideas and give you my two cents.

Filters are meant to capture impurities. That is why we call them filters!

HOWEVER, it requires something to help the impurities get caught in the 'net' of filter material. This is why air purifiers, furnaces, engines and other devices pull the air through them. If you just free hang a filter, it might capture something but it will allow you to utilize the holding capacity (How much contaminates) of the filter to its intended effect.

A furnace filter fan is used to keep large/medium particulates from being drawn into your furnace and damaging your blower motor. We are talking hair, dust, cobwebs and the like. Some filters have better holding capacity but the more you start filling that filter up, the less air flow happens and efficiencies can drop. Making a high efficiency filter with high capacity is the name of the game. Some breakthroughs have been made where the filters are so efficient that the equipment they are made for can't harness their full benefits currently!

I believe outdoor filtering would be a net-negative because your filters will fill with contaminates without honestly providing you with better quality air. You would actually be filling filters and throwing them away without giving yourself a statistical difference?

Does that make sense?

You make paper air filter media, Timothy? Awesome! I was hoping there was someone on Permies who has that kind of knowledge. So my first question to you is, would you compost any of your used air filters? Any fiberglass or plastic based filters are obviously out of the running. But cellulose is compostable. The question is mainly about the additives to the cellulose, if any of those are too nasty to compost? Would there be a way to acquire some cellulose web before the additives are added?

Because I could mimic the pattern of the trees. Put out a big paper filter at the beginning of summer, capture all kinds of compounds that were originally part of a plant, and then drop it to the ground and compost it in the fall. We can't get the magic of photosynthesis to work for us with a dead filter medium. But I figure that many of the compounds in smoke are valuable nutrients for plants if they are in the soil, not in my lungs.

The kite would face into the wind by design. But the disadvantage of a static filter comes from the fact that the wind blows both ways. So particles that are trapped when the wind blows from the north might be blown free when the wind blows from the south. But maybe those particles that blow free will have clumped together with other particles, making them more heavy and more likely to fall to the ground? Maybe at the end of the summer I would have a little pile of nutrient-rich dust on the grass below my filter?

The unfortunate part of filters is that it is hard to know what is actually used to make the filter unless you are the manufacturer.

Most customers have no clue and nothing provided to them to give them an idea. It would be harder to sell filters if people knew that something like titanium dioxide or formaldehyde was part of the process for that particular filter. Its not 'sexy.'

This comes at a cost to this application because even if I knew of a cellulose only filter, it is more than likely to have some kind of resin coating to give it strength and charge.

If I wanted to try and secure some primarily cellulose filtration media, it would be in the realm of food production filtration meant for water applications. That might be your safest bet. Where you would source that would be tricky. I have seen the odd roll of filter material before being cut and put in a filter cage being sold on EBAY here and there.

Personally, I will never try to compost filter material. We are moving towards greener alternatives to the resin chemistry but we are not there yet. The switch to no formaldehyde formulations has been tricky to get the same capacity and performance as partial formaldehyde formulations.  We know cellulose degrades so in production they do their best to prevent that in order to increase filter life expectancy.

Filter fibers are not arranged perfectly straight, they are actually encouraged to be a bit of a random assortment because that helps 'capture' the contaminates. Blowing air in either direction may dislodge some contaminates but it actually trys to cling to them!



This blown up shot shows what I'm getting at. The threads go every which way! They also can be charged with a salt solution in the stock preparation phase to help PULL contaminated in by utilizing a positive or negative charge.

You tend to see filters that have an arrow of which way to use them not because the contaminates will fall out but rather there are multiple layers of increasing microns to help filter from big to little contaminates and capture them in zones thereby increasing capacity.

I will try to pick the brain of our R+D scientists because they are chummy and utilize our line for a lot of experiments and broach the subject. It might take some time because they are busy but I'd be curious if I could get a recommendation on sourcing what we would call "Base Paper" which is the formed paper before a resin application is done in the customer facing market..

It would be really cool to get a hold of some base paper that isn't nasty. I take it that the resin you are talking about is synthetic resin made from petroleum, not tree resin? I wonder if someone some day might experiment with using tree resin to strengthen base paper some day?

Another way to clean the air is to imitate rain. I could set up sprinklers or fountains to wash the smoke out of the sky. All of these methods are going to have a low rate of efficacy. But with how much smoke there is in the sky I really want to fight it somehow.

Hi Jeremy,
I think your desire is good, but I have to agree with a previous poster that to filter the outside air in any significant way, would be very very expensive and very very huge.

Perhaps we can back your desire up a little. What is putting the smoke and contaminates in the air? Sometimes wildfires. I think you could make a more significant difference by getting your property and surrounding properties wildfire resistant. Sometimes factories. How about working on being sustainable and getting your friends and neighbors to be sustainable, which (eventually) would help cut down on manufacturing? Sometimes other. Growing your own food and promoting the growth of plants that will help cleanup the air, I think would give much more effect for the effort.

Jeremy VanGelder wrote:It would be really cool to get a hold of some base paper that isn't nasty. I take it that the resin you are talking about is synthetic resin made from petroleum, not tree resin?

Indeed, a lot of chemicals (Some nasty, some okay ) develop into a coating resin then tends to be activated with either ammonia or industrial caustic. I've seen three ingredient resins and ones that are up towards ten.

For knocking out soot in the air, I would definitely be interested in the usage of sprinklers/misters to snatch material out of the air and bring it to the ground. I'm not sure of the practicality or the energy inputs but that might have better success than a true filter. I know atomized water can be utilized to 'scrub' air in a few different applications. Some industries utilize it to limit formaldehyde/industrial emissions before its vented to the atmosphere.

Something I observed this morning while walking in to work. There was a nice medium-intensity rain falling. And the smell of smoke was strong. Stronger than it has been all week. Now the smell seems to be gone. My theory is that the weather system displaced smoke that had been high in the atmosphere and is actively driving it to the ground, in addition to the rain. Or maybe the rain itself smells like smoke because it has fallen through smoky air?

There are websites that sell little indoor fountains which claim that moving water releases ions into the air which bond with other airborne particles and bring them to the ground. So that idea seems to have a lot of merit, Timothy. Water is just an excellent all-purpose cleaner. Fountains and misters can be gravity powered if you have enough head. The Stanway house fountain shoots 300 feet and 10 inches into the air, all on gravity power. A mister system would probably be more efficient at getting water into the atmosphere. And when I have been near a mister on smoky days there is less of a smoke smell.

I bet a mister system would be the most effective way to clean some air on a backyard scale.

Perhaps we can back your desire up a little. What is putting the smoke and contaminates in the air? Sometimes wildfires. I think you could make a more significant difference by getting your property and surrounding properties wildfire resistant.  

That is a very good idea, Matt. I have been to a FireWise training and have worked my defensible space out to about half of what they recommend. We still have some trees overhanging structures. Thinking in FireWise terms definitely introduces some dilemmas and tradeoffs. "Do I want shade on my house or do I want to live without the risk of a burning tree right next to it?" I am going to plant some shade trees this fall just a bit further outside the defensible space to shade my driveway and reduce the heat bouncing into my house. If I were to hang up any sunshades/air filters between my house and my garage I would have to make sure that I took them down before a fire evacuation!

I am looking at options for replacing the air filter in my heat pump. And I see that "Hog's Hair" filters are one of those options. Most of them claim that they are made from natural material. Does anyone know if they are made from real hog hair?

I do not work in the production of hogs hair filters, but I have done a little digging into my resources.

It appears that hogs hair filters do, at at least once did, contain an amount of true hogs hair. This is mixed with other fiber (I've seen coconut, tree pulp, and a few others mentioned) to create a non-woven filter. A lot of these currently are made of some kind of poly.

Regardless, all of these filters have some kind of chemical resin impregnated to give it longevity and durability. I believe one consideration with hog's hair is that it tends to flex as air is pulled through it. Some people 'reinforce' the filter with metal rods to keep it from being sucked inward towards the furnace when it kicks on.

Thanks, Timothy! I figured that there would still be a lot of chemicals in them. But their washability is intriguing. If I go that direction I will make sure that I reinforce it so it doesn't get sucked in to the blower!