Jim Rooney On The Level

Q. In last Sunday’s paper under the Havens real estate column that I read I saw an article that recommended regular cleaning for humidifiers. The writer said he changed the water daily and disinfected the tank weekly. We have an Aprilaire humidifier on our furnace and no one has ever said anything to us about that. We have our system checked spring and fall and the service man never mentions it. Was the article right?

A. I saw that article too and must say it was confusing. In the first sentence the writer mentioned both a dehumidifier he had and a humidifier on his central air system. Then he went to talk about the cleaning and care of a variety of humidifier types so I looked them up. They were stand alone room humidifiers that you fill with water and plug in the wall.

But before I get too deep into humidifiers I have to give you a look at my history with this column and humidifiers. The first column I wrote about humidifiers was back in the mid-1990s and I said I didn’t like them. I said they tended to be unsanitary. I set off a minor firestorm among some readers who protested vehemently that their humidifiers were kept clean as a hound’s tooth and I was an idiot.

I responded with greater explanation of just why it was that I hold the opinions that I do. This occupied about three columns fairly close together and my editors wondered why I kept writing about humidifiers. I said OK to myself and kept my mouth shut on the subject in the column for years-- but not so out in the field doing home inspections. My favorite anecdote on the subject occurred while I was performing a home inspection for a pediatrician. As we walked over to the furnace-- which had a humidifier hanging off the side of the ductwork about shoulder high- I pointed to it and said “Doc, do you know what that is?” He said “Yeah. That’s a disease distribution system.” “You got it.” I replied.

Let’s think about humidifiers for a minute. When the outside temperature gets low and there is no moisture source in the home the relative humidity of the natural air that migrates into the home and heats to the house temperature of say 68ºF to 72ºF drops to next to nothing. Air that dry makes the air feel cool on the skin as the air is trying to dry anything it can to hydrate itself. Back in the days of hot water or steam radiators I remember my mom filling shallow flat pans of water that were set on top of the radiators for moisture. Some folks would keep kettles on the stove simmering all day to put humidity in the air. The heat of the method of launching moisture into the air kept the process sanitary.

As homes became both heated and cooled through the same means of air distribution-- ducts-- some genius came up the bright idea of introducing moisture into the air stream to elevate the indoor humidity level and the duct mounted humidifier was born. Stand alone humidifiers had been around for a long time and I remember “vaporizers” being placed in bedrooms of sick kids with colds.

Central humidifiers became a great selling point and an HVAC installer revenue enhancer. In the early 1970s the medical profession noticed that people who had central air humidifiers got a little sicker than the rest of the population during winter and children in homes with them took several days longer to get rid of colds. The term they used then was “humidifier fever”. The mother of all airborne moisture diseases got the name Legionnaires Disease. I come from a family of doctors and nurses and they talk shop at the dinner table-- and beyond. I heard about it back then not knowing I would use that knowledge much later.

What researchers found was that not only are the drums, sponges and reservoirs of the humidifiers themselves susceptible to becoming germ breeding pools but even those that can launch pure water -- mist or steam-- into the air stream can be problematic as the moisture at higher levels near the source can and would condense on the inside of the cooler metal ductwork creating a moist plane upon which the microbials can get purchase and grow. I’ve torn ducts apart and seen it with my own eyes.

About a decade or so ago they finally came up with the bright idea of installing UVC sanitizer lights inside of ducts that kill 99.9% of living bugs that pass by one. Problem partially solved because there are millions of central air humidification systems that don’t have them.

As the writer in last Sunday’s paper said you should clean the stand alones frequently but there is only one way I know to keep central systems sanitary but he didn’t mention it.

Keep the mail coming. If you've got a question, tip, or comment let me know. Write "On The Level," c/o The Capital, P.O. Box 3407, Annapolis, MD 21403 or e-mail me at jimrooney@jimrooneyonthelevel.com or inspektor@aol.com.