SIN #1 DO I HAVE A FILTER - WHERE IS IT?
In general all HVAC systems have a filter even cooling only systems. They can be in return air grilles, in the furnace or air handler, in roof mounted equipment, remote duct mounted, multiple filters for 1 system and even multi staged filters (several different types) in one box. You may need help from a HVAC professional to find the location.

SIN #2 HOW MANY YEARS DO THEY LAST?
No filter I know of under normal operating conditions will last a year, most filters will last 3 months under normal conditions, some extra big media style 4" plus width can last 6 months plus. Some high or special use filters may only last a month or less. The only way to know is to check yours often until you formulate a proper schedule.

SIN #3 OH IT'S NASTY DIRTY, YOU TAKE IT OUT; I'LL GET ONE THE NEXT TIME I GO TO THE STORE. WHEN?
That's easy to forget, never run an HVAC system without a filter, blower and or coil cleanings can be very expensive, also leads to plugged up drains which can create condensation floods.

SIN #4 FURNACE FILTERS ARE ONLY NEEDED FOR HEATING!
Oh no the filter in the furnace or HVAC system is almost always for both Heating & Cooling, proper maintenance for both modes of operation are very important. Proper filter maintenance for cooling may even be more important to prevent cooling coil freeze up leading to condensation drain overflow and water damage.

SIN #5 TURN IT OVER USE THE OTHER SIDE
As the down air flow side may appear clean, this only makes the dirt trapped on the other side becoming dislodged when the system starts sending all the previously trapped dirt directly into the system (VERY BAD).

SIN #6 I WONDER WHY THE UTILITY COMPANIES ARE NOT IN THE FILTER BUSINESS?
With out new filters you may use more energy for both heating and cooling.

SIN #7 REALLY EMBARRASSING TO CALL AND PAY FOR SERVICE ON YOUR HOME OR OFFICE JUST TO FIND A PLUGGED FILTER.
The best of HVAC professionals, home owners, and business owners become idiots on changing furnace filters without a written schedule. Trust me it happens all the time.
SIN #8 WHEN WAS THE LAST TIME WE CHANGED IT, I THINK??? UH WELL
Got to have a plan and a schedule, or go on a planned maintenance with an HVAC professional.

SIN #9 WHEN YOU TAKE YOUR FILTER / FILTERS OUT THROW THEM AWAY IMMEDIATELY, THERE NASTY
Awe what size was that again. See SIN #3

SIN #10 WHAT DO I BUY, WHICH ONE IS THE BEST, WILL THIS WORK ON MINE? WOW SO MANY!
Wow there are many different filters on the market they all do many different things. You may need the assistance of HVAC professional to help recommend the correct one for your application whether it is equipment serving, home or at work. Filters have MERV rating, Minimum Efficiency Reporting Value, the efficiency for particle removal.

Tom Tanner
President - Tanner Heating and Air Conditioning
Vice President Air Conditioning Contractors of America Dayton Chapter
Executive board member Home Builders Association of Dayton