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Evelina Zettervall  0:03 

The combination filter for instance will not be helping you on the exhaust because then it's protecting the outside air from gases generated inside or indoors. So no, I would say that for different applications you would have to use different filters and also you want to use the most energy efficient filter for that purpose actually. So if you put a HEPA filter everywhere Of course you will get very clean air but you don't need that clean air everywhere

Dusty Rhodes  0:36 

Hello there and welcome to Let's Talk clean air, our regularly look at how clean air can affect the quality process for you and the workplace. On this episode, we're finding evidence the main types of air filter that are available, what they do and where they work best. My name is Dusty Rhodes and joining me to explain this is Evelina Zettervall. Before joining Camfil HQ in Sweden, Evelina worked as a biomedical analyst and research scientist working with pathogens. Today, she is one of Camfils top experts in air filtration, HVAC and clean rooms as well. Evelina, thank you for joining us on the podcast, we kind of want to go through the five main air filters that are and to find out where they work in the process and things to watch out for when we're considering which filter to use, and what kind of industries use them as well. Perhaps we could start off with pre filters, can you tell me what a pre filter is, and where it is used in the process?

Evelina Zettervall  1:32 

Thanks Dusty, let's start by looking where they are located and the name pre filter sort of tells already that it's a filter that you put in front of the main filter. And the main function is to protect the main filter from really large particles. So it will collect and gather the large particles in front of the main filter.

Dusty Rhodes  1:59 

And why is it is it always important to have a pre filter before the main filter?

Evelina Zettervall  2:05 

Well, it depends on the air coming that direction. So it's really if you have a heavily polluted air, it could be a dusty process, or it could be outdoor air in a really dirty area. So large city, ambient air that is coming. So really to protect the fine filters from the larger particles in the air coming there.

Dusty Rhodes  2:31 

Okay, and if you're looking for a pre filter, what are the kinds of important things to keep in your mind when you're considering which one to want to get?

Evelina Zettervall  2:39 

Yeah, it's important that you will have a pre filter with a long life and high removal capacity. So you make sure that you don't clog the filter, but it can last over time, without building up a lot of pressure. Also, a sturdy design is helpful. We've seen a lot of pictures of panel filters collapsing in their handling systems. And if you have a good design and a robust product, it will last longer.

Dusty Rhodes  3:13 

So pre filter is kind of  like a bouncer at a nightclub is it's kind of like the first line of defense And is this us then in all kinds of industries? Or is it only is very specialized ones or are very heavily polluted areas?

Evelina Zettervall  3:34 

Now it's, you can see it applies to all industries. It's mainly the application with large particles and very dusty air. So it's more about the polluted air than the application itself, could be both in the industry, but also in the general ventilation.

Dusty Rhodes  3:54 

Now, I know it's impossibly hard to say how long that a filter will last in your experience for somebody who is in a say, city situation where pollution levels are higher, and in an industrialized area. So like I'm thinking heavy usage, how long would a pre filter would you expect a pre filter to last would you have to replace it every year, every month every week?

Evelina Zettervall  4:18 

That's different. I can say that in general ventilation, where you might have like a panel filter, it's often replaced several times per year. While if you have a pre filter that is in an industrial process, it could be a different type of pre filter. So it could be a bag filter that is really made for collecting a lot of dust that could last longer than also maybe an annual change or something depending on the application. Okay,

Dusty Rhodes  4:49 

well let's move on to dust and finer particles and talk about maybe a fine filter as well. Is this used in the pre stage or as a main filter?

Evelina Zettervall  5:0

It could be both. If you have a industry that demands very clean air, like life science or hospitals, you can have fine filters in several steps. But in general, the fine filter is there to protect humans from really small particles in the air. So it's about high removal of smallparticles that could easily enter your bloodstream.

Dusty Rhodes  5:28  

And how do you describe the size of these particles? How small are they? 

Evelina Zettervall  5:35  
Yeah, we have like different fractions in the ambient air that we look at. So we have ePM1 is the smallest fraction, and that is actually particles that are one micrometer, or smaller. So it's a, it's a mass of particles, but all the smallest particles,

Dusty Rhodes  5:51  

and where should you consider using a fine particle filter,

Evelina Zettervall  5:56  

you should have fine particle filters whenever wherever human is located. So if you have office buildings, public centers, wherever anyone is staying for a longer time, you need to have fine filters in the ventilation system.

Dusty Rhodes  6:13  

And Evelina. What makes a good fine filter.

Evelina Zettervall  6:19  

I mean, to be able to catch the smallest particle in the air, we normally if we look at a glass fiber filter, we use a big mixture of small and bigger fibers to be able to really catch the smallest one. And when you do that, you will have a quite dense media, which is also correlated to high pressure drop. So what is really important apart from the high removal efficiency is that you have an energy efficient filter as well. So with the construction that are the sign that it will have the lowest possible pressure drop as well as high removal capacity.

Dusty Rhodes  7:01  

And the pressure drop is quite important as well, when it comes to the energy that has been used by the entire system. All right,

Evelina Zettervall  7:08  

exactly. And if you look at your event, energy classification, for instance, we have energy ratings going from A+ down to an E grade. So it's important that you select the filter with a high energy class two.

Dusty Rhodes  7:26  

Is there a big difference between a plus down to E?

Evelina Zettervall  7:29  

Yes, of course, i you calculate the number of kilowatt hours used annually by the filter. And if you look at the A+ filter in this specific filter class, that could be for instance, ePM 1 60%, you don't get to use more or consume more than 850kw/hr per year

Dusty Rhodes  7:54 

So much as we would buy electronics or household goods that have got that rating system The same goes for the filters on the energy rating. Exactly. All right. Okay. And tell me then finally, about a fine filters, what type of industries typically would use them? Can you give me an example?

Evelina Zettervall  8:13  

Yes, as I mentioned in the beginning, here, the for instance, hospitals is very important that you have a really good presentation before the actual operating theatre or also to the waiting room. So that's one of the applications where you would need to steps or find filters actually to really treat there. But in general, it's more typically used in offices and public buildings and so on. Okay,

Dusty Rhodes  8:41  

let's move on to HEPA filters and HEPA I suppose are the big daddy of a filtering because well, they're the most famous anyway. And there are two kind of main HEPA filters you've got the box filter and the panel filter. Can you tell me firstly about the HEPA box filter where in the process does that get used?

Evelina Zettervall  8:59  

Yes, the box type HEPA are the high airflow HEPA actually. So we're normally we find them upstreams in the process. So it treats the air already in maybe the air handling system or in a filter housing upstream where you need to treat and filtrate a lot of air

Unknown Speaker  9:20  

and where does it get the name box filter? 

Evelina Zettervall  9:24  

Yeah, it's shaped like a box. So it's with the flat edges and so on so it fits into the housings as well. You can also use it on the exhaust air so it's not only on the supplier so if you have something that is very harmful in your process, you put also the box type helpers normally on the exhaust there,

Dusty Rhodes  9:49  

as well as thinking of particles that may be escaping a facility and going out into the general air and putting a filter on that that exit. Does it also handle odor?

Evelina Zettervall  9:59  

No,  it's only a particle filter is to be able to handle odor or gases, you need to have a carbon filter or molecular filter added into the process

Dusty Rhodes  10:10  

. Okay? So why then what was the importance of a HEPA box filter? Where do you recommend that

Evelina Zettervall  10:19  

I will recommend it whenever you have a process that is very sensitive, it can be a manufacturing process, for instance, or it also could also be where you need to protect humans, like in hospitals, and for the environment, if you have something dangerous in your like particles that are dangerous in your process, and you can't release them to there. So for instance, the pharma industry, when they are handling toxic, toxic substances, you need to make sure that these substances doesn't reach out to the environment and also protect the humans there.

Dusty Rhodes  10:57  

Let me ask you kind of how do I make a decision about which HEPA box filter to get if I if I have five in front of me from different manufacturers? What should I be watching out for on good features to have?

Evelina Zettervall  11:10  

Yeah, first of all, needs to be leak free. And that's really important when it comes to HEPA filters, because the efficiency of these are really high. So you need to make sure that it's leak free. So normally, we test all our HEPA filters, and it comes with a test protocol or scan test protocol that makes sure and give some proof that it's leak free.

Dusty Rhodes  11:34  

And when you say leak free and having a very high percentage, how high is that percentage?

Evelina Zettervall  11:39  

If you have an h 14, for instance, one of the grades it's 99.995 percentage of the specific particle size.

Dusty Rhodes  11:50  

And again, then can you give me a type of industry then that would use a HEPA box filter specifically?

Evelina Zettervall  11:57  

Yeah, the pharma industry, for instance, is a good industry or a good indication of where it's used.

Dusty Rhodes  12:04  

Okay, well, you need very, very high level.  
So for cleanrooms, anything to a pharma, or maybe computer data center, that kind of thing, is it?

Evelina Zettervall  12:11  

Yeah, it's I mean, cleanroom, they are more having the panel type filters. For the high airflow parts and the exhaust part.

Dusty Rhodes  12:24  

So for the clean rooms, where you also need to have very high levels of clean air, a panel filter is the thing that will be used more often, we were mentioning percentages, is there a percentage difference between the effectiveness of a half a box filter and a HEPA panel filter.

Evelina Zettervall  12:44  

Now there's no difference in the actual efficiency. But the difference is that panel filter is used in a terminal housing, so it's located in direct contact with the cleanroom. So you make sure that you have the absolutely last step of the the filtration or the ventilation is the HEPA panel. So you control the supply air by putting the HEPA panel in the ceiling of the cleanroom.

Dusty Rhodes  13:14  

And that is the very last stage of the process for their for the HEPA pass,

Evelina Zettervall  13:17  

actually, so you eliminate the risk of anything happening after the HEPA filter into the room. Any allowed leakage or whatever. So you, you put the terminal HEPA there, and then you scan and prove that it's leak free in the installation. So no particles is entering the room.

Dusty Rhodes  13:38  

We said leak free was very important. What I take a leak free is also important with HEPA panels. What other good features should we look at when we're thinking about a HEPA panel filter?

Evelina Zettervall  13:52  

Yeah, the HEPA panel is even more important to be leak free. Also in its installation. All HEPA panels that are installed in clean rooms, for instance, are validated. So we make sure that the integrity is proven. And to be able to do that you need access to the filter surface. So you can scan with a probe indirect like a couple of centimeters below the filter surface. So it's even more important here.

Dusty Rhodes  14:25  

So we've been talking about pre filters, find filters have a box HEPA panel filters. Finally, we come to a combination filter is a combination, a combination of always spoken about or is there a twist?

Evelina Zettervall  14:39  

There's a twist actually, because when we say combination filters in this particular chat, we talk about where we have a filter with combined media both for particle removal but also for the molecular removal. So it's combined glass fiber and Carbon media. So here we come into the part where we can also remove the smallest particles that are even molecule molecules or gases. So if you have odors that you want to get rid of, or if you need to filtrate out VOCs are anything coming from outside or in the process that needs to be removed. So a gas in particular?

Dusty Rhodes  15:28  

So is this one of the most sensitive of all the filters?

Evelina Zettervall  15:34  

Yes, I mean, the combination is there, because you need always to have particle removal in front of carbon media, so to say, so if we don't combine them, we have them in separate stages, you can have molecular filter, but then you need to have a particle filter in front of that. But when you combine the these two medias, you can have them in one filter step. So it's where you have, for instance, traffic outside, and you need to get rid of the part of molecules or gases from the traffic, you could instead of inserting a bag filter, you can insert a combination bag filter that will remove the gases out of the air as well.

Dusty Rhodes  16:19  

So does a combination filter offer extra protection? Or is it designed to do two jobs in one unit?

Evelina Zettervall  16:27  

It's both actually, it would offer you more protection where you have gases in the air. But it's also combining two steps, because a lot of times, it might not be possible to rebuild the ventilation. But yes, it will offer a higher protection.

Dusty Rhodes  16:48  

And if again, if I'm looking at a combination filters, what should I keep in mind, what's important about making my decision on which one to choose?

Evelina Zettervall  16:57  

Yeah, it's sort of a relates back to the molecular filter, molecular filter is very important that you have the fit for the purpose. So if you have, for instance, odors that you want to get rid of, that might be useful to test and see if you can just insert a combination filter instead of your regular bag filter or compact filter. But if you have a heavily polluted air coming in, so you have a high concentration of the gas, that will not will not help you, then so dimensioning is very important. And make sure that it's enough molecular media to to be able to remove the gas,

Dusty Rhodes  17:43  

is it a little like layering, where if you have a light use a combination filter is perfect for you. And then the other extreme is if you have a very, very heavy use, you should have a combination filter. In addition to the other filters you have,

Evelina Zettervall  17:58  

I would say that combination filter is always a light use. Okay, so if you have a higher need or a more heavy duty application, the combination filter will not fit for that perfect purpose. So then you need to look at something else.

Dusty Rhodes  18:17  

Last question for you Evelina. They are the main the five main filter types. If I wanted to be extremely careful about the air that is coming into my facility, why don't I just pick the best of those five and put it everywhere? So I just have the best filter in every chain of the process? Do I need to have the various different types of filters in my system?

Evelina Zettervall  18:40  

Yes, I would say they fell different purposes. So you can put the pre filter everywhere, but somewhere you need to have the pre filter to protect the other ones, the combination filter, for instance, will not be helping you on the exhaust, because then it's protecting the outside air from gases generated inside or indoors. So now I would say that for different applications, you would have to use different filters. And also you want to use the most energy efficient filter for that purpose actually. So if you put a HEPA filter everywhere, of course you will get very clean air but you don't need that cleaner everywhere. And it will come with a high pressure drop that will increase the energy bill a lot.

Dusty Rhodes  19:28  

Well, Evelina. All of that is a fascinating, I wasn't aware of the various different levels and all of the various uses of the filters and thank you very much for filling us in just on the basics of how it all works. If you'd like to find out more about air filters, just follow the links in the show notes, which you'll find in the description of this podcast on your smartphone, or whatever device you're listening to us on today. Our podcast was produced by Camfil, a world leader in the development and production of air filters and clean air solutions. If you'd like to stay to date on how plein air can affect the quality process for you and the workplace. Do click follow or subscribe in your podcast player and you will get our next episode automatically. Until then, for myself to serious thank you as always for listening and take care