Do you know what's lurking inside your furnace? Or better yet, what's right in front of it? I'll give you a couple of hints: Bacteria, dust, allergens, pet fur, mold and other particularly nasty substances.

I'm sure there are plenty of people reading this who are telling themselves: "This isn't the case in my house, I'm a good housekeeper, I keep the entire place clean, tidy and sanitized." Guess what? That doesn't matter. When your furnace is operating, it's sucking up airborne particles that are so small you can't even see them, let alone clean them. Unless you run your home like an intensive Care hospital ward, I can guarantee that you do have plenty of contaminants floating around your living area.

Filltrete Replacement Furnace FilterBut there is a super easy, super cheap solution: Replace Your Furnace Filter. In most cases you can pick up a replacement furnace filter for about $5 to $10. And if you want a really fancy, super-dooper, "filters out almost everything" kind, you can still find them well under $20. seriously. Twenty bucks. And that's for the absolute fanciest types. You can even buy them online at Amazon and save even more, often by buying in bulk.

Dollar for dollar, it's one of the absolute best investments you'll ever make. And you should make that investment fairly frequently. By most accounts, you should replace your furnace filter at least once per year, particularly in late summer or early fall, just before you start firing it up for the colder weather ahead.

I'm sure some of you aren't sold on the idea, or aren't convinced that a measly ten bucks is worth your time, effort and money. If that's you, then this next section is just for you:

Top 5 Reasons To Replace Your Furnace Filter Regularly

1. You will save money.

That's right, you can actually turn a dollar-for-dollar profit when you replace your furnace filter. How? Because the filters get plugged up as they prevent all the gunk from going into your furnace (and thus re-entering the air you breathe). And as they plug up, it restricts the airflow. This restriction causes your furnace to work harder to suck in enough air to operate effectively, and because less air is traveling into the furnace per second, it must stay on longer to heat enough air to keep you and your family warm and toasty.

How much you'll save is dependant on several factors, but I can almost guarantee that you'll "make your money back" within a month or two. And since most people run their heaters for several months in the winter, you're actually turning a profit. A nice, juicy profit at that. Who wouldn't pay $15 to save three, four or even five times that amount in lower utility costs?

2. You will breathe better.

Did you know that properly filtering the air that circulates around your home could aid your nose and respiratory system? It's true. All of the gunk that I mentioned earlier in this article is present in every home, no matter how meticulous of a house keeper you are. And when the furnace is working hard in the cold winter months, it's sucking all of that stuff through your ductwork (where it can latch on and multiply), then it heats it up and blows it right back into your living areas. Have you ever blown on a dusty counter top? What happens? The dust goes everywhere, right? That's exactly what your furnace registers would look like if you could look close enough. It's worse in the winter, because your house is typically closed up tight, and you're just circulating the same air over and over again, thus you're blowing around the same microorganisms and dust over and over again, too.

We all know that dust and other allergens aren't exactly great for our bodies, particularly those with breathing problems like asthma. So buying a replacement furnace filter that's designed to catch even the smallest allergens is always a smart choice. Even if you breathe just fine, it never hurts to make your home a little cleaner and healthier.

3. Your furnace will last longer.

Furnaces aren't cheap, so it only makes sense to keep yours running trouble-free for as long as possible. Replacing the furnace filter is one of the easiest, yet most important steps to keeping that big, expensive appliance operating smoothly, efficiently and trouble-free. The more plugged up your filter becomes, the harder the unit needs to work. The harder it works, the faster it wears out (it is a machine, after all). Think of it like a car, keep up on the routine maintenance and it will last for years; but neglect the little things like oil and filter changes and you probably won't be driving it for very long.

Again, what's a couple of bucks (to replace your furnace filter) in the larger scale of replacing a furnace, which will cost several thousand dollars itself, plus at least another thousand bucks in labor?

4. It's easy.

It's actually super, dooper easy. If you've made it this far but are worried about how difficult replacing a furnace filter really is, this should make you feel much better. In almost every furnace, the filter box is easily accessible and is "user serviceable." That means you aren't expected to pay a professional to come out and take care of it, the manufacturers actually designed these things for men and women like yourself, who aren't professional heating and air conditioning professionals driving around in big HVAC vans.

Most furnace filters take about 10 seconds to replace. It might take a bit longer if it's your first time, since you'll have to walk your way through this brand new process, but I would expect it would take any longer than 10 minutes for even the most novice DIY guy or gal.

Always read through the your furnace's owner's manual before doing this, and follow every precaution it outlines. I'm not going to go into the process of actually replacing your furnace filter here, so read your manual (it's required by law to be on or near the furnace at all times). If you're really nervous, call an experienced friend or professional to walk you through your first time. Once you see how it's done, you'll be able to do it yourself over and over again.

5. You will feel accomplished.

Nothing beats that feeling of accomplishment, when you know you've just done something that will pay off in dividends for months to come. And knowing that you did it all by yourself, well, that makes you a bona fide home improvement expert now, doesn't it? Maybe not, but you'll feel like that for at least the remainder of the afternoon.

Furnace Filter Replacement Cautions

Okay, the last word. The "fine print" so to speak. Always read your furnace owner's manual carefully, as well as any instructions that come with your new filter. Make sure you follow all safety protocol, such as flipping any necessary circuit breakers. Replacing a furnace filter is cheap and easy, but you are dealing with a very powerful utility appliance, so heed all cautions - now go out and get it done!