I have a 22-year-old central air unit in my home. I'm running the fan 24/7 because my dog has COPD. (Use top of the line 3M filters.) Would there be any danger of fire from running the fan continuously in this older unit? Is there any basic maintenance that should be done to insure the fan's safe operation?

I'm away during the day for work. Don't want to take any chances.

The units are basically designed to run all the time so as long as it intake and supply ducts/registers are open you should be fine letting it run all the time.

The 3M filters are highly restrictive which could cause a problem with the fan motor. I would strongly suggest the installation of either an electronic or a 4" media filter. That being said, duct sizing & filter maintenance play a huge role in fan motor longevity as well.

Yes there is reg maint. Check for oil ports on either end of the moter and clean and vacume it out. The TOP OF THE line filters ONLY catch the dust that happens to get to the filter not a lot in the grand sceem.and when your running heat they do clog and slow the air flow quite a bit and will cause the unit to overheat . As for A/C it will cause ice to form on the coil... to make the answer shorter a reg pleated filter will do the same job for your dog ( as most dust getting to him is near the floor and you air filter is high. Ive been a hvac tech for 24 years the cost difference is not worth the damage to your system. And to boot running a high effy. Filter as it clogs air flow reduces, air flow reduces it harder the exchange air.. all equels higher gas and elect bills... good luck to you and your pup

Thanks guys for taking the time to respond. Very helpful. I'll probably have a professional take a look at it just in case. Also, I wouldn't have guessed that the best air filters may do more harm than good. I'll run these a few weeks to recover some of the expense, then switch to something more middle of the road.

Good idea. I know what it's like having a dog that is not well. Best of luck with the pup.