Well, its back. The smell. Every Monday morning. This week, worse than its ever been......

AHU- 25 HP motor on a speed drive.....hot and cold water/air coils. Conventional (blanket) filtration....(yes, in excellent condition and changed quarterly)

Problem began about 2 years ago. The typical complaints......stinky....sour milk, dirty socks smell. At first I could not smell it. Now, not so much.

Once we realized we had a problem, I began cleaning the coils. Removed a bunch of lagging which appeared "moldy". (had the industrial hygenist from our risk mgmnt. department take some tape samples, results were that there "was some mold present", however; the lagging did not have an odor. It was determined that this (the lagging) had a mold that occurs everywhere, but was concentrated due to the large volume of air passing over it.
I was taking a class at the time, and this website was mentioned, so my search for information began.

First, I rescheduled the AHU to run continuously 24/7, instead of 0400-1159 x 5 days. This did seem to help. However, we began to notice that the odor did not manifest itself unless the chillers were running......AHA!

So, thru some research called internet surfing, we have learned that its the moisture triggering the "blooms".

At first, cleaning the coils had little effect, except to "overcome" the odor with the odor of the cleaner. However, a pattern emerged which is consistent to this date. Monday mornings, after the coils have been dry since friday nite, they get wet, and the smell occurs.

These chilled water coils, CU to CU, are about 13" thick. I could not see water coming out of the other side, even when we used a power washer, wide tip. So, purchased a dedicated coil cleaning machine.....Goodway CC-600. What a great piece of equipment!

Came in on a sunday, used the "evil yellow foaming" coil cleaner first. Was advised to clean in the opposite direction as the air flow. I went thru 4 gallons of that stuff, and still could not get the solution to come out the (upstream) other side. Then came the bleach. (I know, I know, but I was careful and did not let it sit too long). Rinsed x 4. Completely. Ran the system, and it was fine for about 3 weeks.

This monday, wow, it was bad.
So, my next step: Clean them again with the foaming cleaner, from BOTH SIDES. I will then bleach them again, rinsing generously of course.

Got a quote of $40K to replace the coils, Im here anyway so cleaning the coils is a much cheaper prospect to the company.

I dont want to have to worry about this stuff forever, so Im gonna give it one (or 2) more tries before I recommend replacement.

Any thoughts or suggestions?