If you are like me, you are interested in the truth.  But when you go down the rabbit hole, things start to look very grey.

Take furnace filters for example: I was at Home Depot and I was staring at wall-to-wall furnace filters. The prices were all over the place, from as low as $3.00 and going well over $50.00 for a single filter. And as a price, but also value-conscious consumer, I pulled up my phone and started Googling air filters. Then, in frustration, I bought a mid-level multi-pack. It is impossible to find a true answer, because everyone has stakes in the game.

Home Depot employees would tell you, buy the HEPA-whatever because the store makes more money on it. An HVAC (Heating Venting Air Conditioning) specialist would tell you that all those filters are crap and what you need is an auxiliary system to scrub your air clean (for over $1000.00). Who is going to tell you the truth?

I will tell you the truth. Well, as best as I can ascertain.

How Your Filter Works

Before I tell you what to buy, I would like to teach you what is happening in your HVAC system, assuming you have a forced air system. If you have a boiler system, then open a window.

When your furnace turns on, air is drawn into the system (from an outside vent and also though large inside air-return vents) through the air-return ductwork. It is that large circular or rectangular box that runs along your basement ceiling. The air passes through the filter that is mounted between the air return and your furnace / central air unit, and through the blower inside the furnace, where it is either heated or cooled or just blown again. It is then forced through your house through smaller pipes (to increase pressure) and then through registers mounted in your floor or on the wall. And then sucked back into the air-return and through the system again.

The Filter

A filter is basically a screen that picks up debris particles as they pass through the duct work and into your furnace. The tighter the screen, the smaller the particles your filter can theoretically trap.

The cheapest quality filters are flat fiberglass screens. They will pick up a bit of material, like leaves, or cat hair. Next up is a flat material screen made of either polyester or cotton. These are designed to collect mold spors, dander, dust, pollen, etc.

To increase surface area, manufacturers can then pleat the cotton into v-shaped accordions, which will dramatically increase the surface area of the screen, while still being made of only cotton. Like tank armour, the air also has to pass through a diagonal surface, meaning that it is going through more material than on a flat filter. On top of the pleated screen, it can be electrostatically charged, the cotton or polyester weave can be tightened or the pleats can be deepened until they get so thick that you need a separate box to run them. What I have come to learn that regardless of how effective it is, manufacturers of filters will always want you to drop more money on costlier filters.

There is a ROI problem that starts to crop up the more you spend on filters. The thicker / tricked out the filter is, the harder it works your furnace. You need more pull to pass the air through the filter and back out of the system again. So an expensive filter is actually harder on your furnace / forced-air system. Replacing an air system in your house is one of the most expensive things you can do.

The filter technically also needs to be fitted with very tight tolerances for the air not to bypass the filter by going around the filter itself. Try inserting a cardboard framed filter without bending or mashing the cardboard at all. In my case, the previous owners also left the nail heads exposed on the inside meaning that I also have to be careful not to shred the filter as I install it as well.

And in the end, how well does the filter really work?

Other Considerations

The whole process of cleaning the air in your house is assuming a number of details. The particles need to be pulled into the air return vents (which have very low pressure) to actually do anything. The farther the particles are from the vents, the less likely it is going to go into the furnace to get scrubbed.

Are your vents, air ductwork, etc. a sealed system? Is there holes and cracks in your ductwork? Is everything taped off so that only the air coming in through the air return can travel through the system. A leaky system is a poor performing system.

Is your duct work dirty? Do you already have a dust and who-knows-what ridden duct system? It is unclear how effective cleaning your duct work is, but it isn’t a bad thing. According to the EPA:

Some research suggests that cleaning heating and cooling system components (e.g., cooling coils, fans and heat exchangers) may improve the efficiency of your system, resulting in a longer operating life, as well as some energy and maintenance cost savings. However, little evidence exists that cleaning only the ducts will improve the efficiency of the system.

You may consider having your air ducts cleaned simply because it seems logical that air ducts will get dirty over time and should be occasionally cleaned. Provided that the cleaning is done properly, no evidence suggests that such cleaning would be detrimental. EPA does not recommend that the air ducts be cleaned routinely, but only as needed. SOURCE


  • Clean your duct work if needed by a reputable company (Google them)
  • Tape up the holes in your system using Air Duct Aluminum Foil Tape (not to be confused with Duct Tape)
  • Vacuum your house regularly
  • Don’t install wall-to-wall rugs as they collect dust and allergens.

The Right Filter

This is what I have come to learn: Buy a multi-pack of branded pleated filters and change them often. Most people forget they even need to change their filter. By buying a pleated cotton/poly filter, you get the best bang for your buck. Not too expensive, but the pleats increase the surface area. And at a mid-range price, it won’t be too dense to over-work your furnace. And if you change your filter often, you will have a filter that “breathes” efficiently since the air will go through the filter, rather than bypassing it because it is full.


If you notice your filter is exceptionally dirty or you have allergies, change it more often. And put it into your Google calendar. Make it a re-occurring event.

How Does This Relate To Survival?

You can only live without air for roughly 3 minutes. You breath an average of 15 – 20 breaths a minute for your whole life which is like 7 billion times in a 70 year lifespan. Air quality is important for your health. Poor air quality is linked from allergies all the way to shorter life spans.