Air Conditioning - Fear of getting Legionaire's disease through a/c!

[Legionaires (sp.)]

It comes from some bacteria that gets drawn through the cooling vents, most likely as the air is blown through the evaporator coils and condensate water in the pan below it.

Wouldn't you think that if Legionaire's disease can develop in this situation, that it would turn up more often than it does? It would be good, therefore, to better understand why it occurs, where other times it does not.

As long your drain line are clear, and the water drains away from the coil, no fear is needed. Also, keep the air filter in place and cleaned..


If you smell an off order, the coil is maybe due for cleaning.


I have a media air filter, and UV light above the A-Coil, I am good.

You don't have the correct enviroment in a residential a/c to breed Legionella. It's normally found in cooling towers.

Way to cold for legionaire's! The water would have to be warmer and standing still for a while! Then you would have to be able to get it air born very hard to do with 1200cfm blower 2 feet above pan!

Legionella would not be a problem in a residential a/c as everyone says.
Commercial airconditioning cooling towers are where this illness became noteworthy but this is only one source.
Legionella is a natural occuring bacteria that can be found nearly everywhere.
What it takes for it to grow is water at a temperature range of between 45 and 140 degF.
When it grows in water it needs to be aerosolized and then inhaled to infect a person.
An a/c cooliing tower is the perfect source to cause an outbreak because the water in them is warm and the large fans then turn the warm water into a fine mist.
Another common but not as well known source of legionella infection is a domestic hot water tank.
Tanks that are well below 140 degF are a prime breeeding gound for legionella and a shower head will atomize the water that will be inhaled when showering.
Not to worry though, the strain found in hw tanks is of a milder variety and people who have a normal imune system will not be bothered by it.

Search (http://www.google.ca/search?hs=2tf&hl=en&client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial&q=legionella+infection+sources&btnG=Search&meta=) for Legionella info.

So if it is the cooling tower, then that air would somehow have to get back in the building. Because cooling tower air is not directly circulated back into the building. Maybe that there is so much of this bad air/mist whipped around in the area that it enters through vents on the roof or windows?... or, in some cases, if the 'cooling tower' is located near a fresh air intake of an air handler unit? It be interesting to find out what the HVAC mechanical design of these building that have had Legionaire/s, are like.

Most "but not all by any means" commercial buildings incorporate water treament in their open and closed loop systems. One of the treatment chemicals in the open loop is either liquid or tablet forms of Bromine. It's like chlorine but don't evaporate out of the water as fast. If kept at the proper levels it kills legionella. A good practice is for the water to be tested by a lab two or three times a year for legionella to see where you stand. Like Greg says there are several different strands of legionella but there's only one or two that cause Legionares disease.

There is a pretty good explanation of how Legionella enters cooling towers and an illustration at http://www.ccohs.ca/oshanswers/diseases/legion.html

Although some cases of Legionaire's Disease have been traced to home plumbing, most occur in large buildings. This is likely because of larger and more complex plumbing systems and the use of cooling towers where warm water can pool and grow bacteria.

twelvepole,

I read the whole thing. And it was at the last paragraph where it said that intake ventilation should not be close to the cooling tower.

I took care a of a commercial building that had a cooling tower like the first pic shown. There was no fresh air intake 'near' it. It was located down the side of the building. But, I suppose under the right situation, you could always have airborne particles coming from anywhere and going anywhere.

I wonder if Legionella is an oustide thing (they mentioned about the soil and how disturbing the soil that contains it can also raise problems) more, and that is why houses don't have it gather in the condenstate pan under the a-coil above the furnace. Say that the pan was plugged and the residents stopped using the a/c during some part of the year, while the pan had stagnant water in it. And then at some later date, they turned back on either the furnace, fan, or a/c. That was sort of my concern.

But since this doesn't happen, or is very rare?..that maybe basements aren't good breeding grounds for Legionella under even stagnant water conditions. And that is nice to know, if that is the case.

In the cooling tower I had, we had pigeons doing their droppings inside.

Legionella bacteria occurs naturally in the environment, usually in water. Like mold & mildew spores that are everywhere, they tend not to be a problem until they find the right conditions for settling in and growing. Legionella likes warm water like in cooling towers, hot tubs, large plumbing systems, water systems on cruise ships, and parts of air conditioning systems in large buildings. Car and residential air conditioning systems tend not to pose a problem. Residential water heaters may pose a problem if temperature is 122 degrees or less. Because the bacteria must enter the lungs through aspiration, showers tend to pass along the bacteria from water heater.

So much for wanting to turn water heaters temp TOO far down...eh?