Thursday, September 25, 2014

When to Clean your HVAC system(s)

When to clean?  When to clean?  Do you even need to clean it?  Well it has been something of a controversial subject for many years.  Personally I find the concept that it does not require cleaning to be ludicrous, ridiculous, brain dead and/or any other expression of something just being stupid on its face.

Not since Ignaz Semmelweis, Hungarian-born physician began pushing physicians to wash their hands before delivering babies, has the idea been accepted that cleaning something is just unnecessary.  Dr. Semmelweis observed in 1847 that the death rate of women from childbed fever was significantly more frequent in women assisted by medical students than those by midwives.  He observed that medical students would often assist in birthing after performing autopsies on patients who had died of sepsis.  Dr. Semmelweis instituted a strict hygiene policy of hand washing with an antiseptic solution.  Deaths of women resulting from childbirth dropped dramatically.  Of course he received his “just rewards” from the scientific/medical establishment, because everyone knew it was “settled science” or “consensus science” that hygiene or washing hands had nothing to do with infection.  Dr. Semmelweis persisted and finally won the day, but began suffering from depression due to the continuous criticism.   In 1865 he was admitted to a mental hospital where he died two weeks later at the age of 47.  And wasn’t it Galileo who was imprisoned for disagreeing with the established science of the day?  They called it heresy.

As for me, I tend to agree with Michael Crichton, the mega-successful novelist, “There is no such thing as consensus science.  If it’s consensus, it isn’t science.  If it’s science, it isn’t consensus. Period.”

And this brings us sort of circuitously to cleaning of HVAC (Heating, Ventilating and Air Conditioning) systems.  It could be I’m a bit behind the times, so maybe the powers that be are no longer playing the tune that HVAC systems do not require cleaning.  If you believe that, you should see some of the pictures of duct interiors before and after cleaning.  You wouldn’t want to breathe air that flows through some of those ducts.

Maybe it’s Hollywood that is causing the confusion.  Surely you have seen celluloid heroes escaping or hiding or being chased through ventilation ducts.  Those ducts are so clean you could eat your scrambled eggs off them.  The heroes come out of those ducts without so much as a smudge on the knee of their trousers.  Now juxtapose that picture with how workers look who have actually “crawled” larger ducts cleaning them by hand vacuuming.  I could tell you some stories – or show you some pictures.

Even with good filtration, there are often situations with filters not fitting snuggly so there is some air that bypasses the filters.  Some small particulate including bacteria and mold spores can actually pass through the filters unless they are HEPA (High Efficiency Particulate Arresting) filters.  Filters do break down and particulate can actually come loose from the filters and blow downstream.  After years of just this particulate, ducts can become quite dirty.  Evaporative coils become wet during cooling season.  Moisture with any organic particulate and mold spores is the combination needed for mold growth.  So not just particulate, but mold amplification can also be a problem.

Hopefully I have at least made you somewhat amenable to the idea that HVAC systems need to be cleaned every now and then.

All right!  How do you know when to clean them? 

1)        My rule of thumb is that the entire HVAC system should be cleaned ever five to eight years based on their environment and use. 
2)       If you move into a house or building that has been previously occupied, you are inheriting the life style of the previous occupant.  This makes cleaning a prudent activity.
3)       If you have been in a house or building for few years and don’t remember if the HVAC systems have ever been cleaned.
4)       If you come into your office in the morning and regularly find gritty or fibrous dust on your desk.
5)       If you see black material caught in ventilation supply grills.
6)       If air handlers are replaced but installed using the existing ducts.  (More powerful airflow from the new unit is likely to dislodge and blow particles downstream into the occupied spaces.)
7)       If there is a lot of coughing and/or sneezing in your office area.
8)       If people complain of watery or itchy eyes. 
9)       If you notice musty odors especially when the HVAC system first comes on.
10)    If you have product open to the air that could become contaminated.

Of course, if you aren’t sure if your HVAC system should be cleaned or if it is worth the investment in cleaning, you can get a free estimate from Air Duct Cleaning that will include photos to document the current condition.  If you select to have the systems cleaned you will receive after pictures to show the contrast between before and after complete and proper cleaning.   In areas of the country that are not Southern California, insist on inspection and written estimate that includes pictures to verify the need for cleaning.


  1. The fan in my HVAC system isn't working anymore. I think I overheated it last week. I left it on for a long time because it was just so hot outside.

  2. Where do you live that it was so hot in December that you overused and overheated your fan?

  3. Duct Cleaning could be the healthiest home improvement investment you will ever make. Heating, ventilation, and air conditioning (HVAC) systems have been shown to act as a collection source for a variety of contaminants that have the potential to affect health, such as mold, fungi, bacteria, and very small particles of dust. Your HVAC system's heating ducts should be cleaned periodically to allow efficient heating and provide fresh, clean air. I used the HVAC Cleaning service; one of the easiest ways to cut electricity costs is to make sure your home has proper insulation. In addition, ventilation is important as well.

    1. Well said. And keep in mind that if you move into a previously occupied residence, you need to clean the HVAC system. You are inheriting the lifestyle of the previous occupants.

  4. Your blogs seems quite interesting though little bit dragging, thanks for instructions on when to clean HVAC system. I never had a serious thought of this. Hygiene is of course is important for a healthy living. A lot more has to be considered while Setting a HVAC system. You can log into Chemtrols for more details on the system.

  5. Sorry if my articles are dragging. Some of what I do is for my own amusement. I also often try to make points on other or related subjects.