Negative is Really “Negative”
Negative is Really “Negative” – By Doug Long, ASCS
I was having lunch with one of the HVAC contractors that we often work with a couple of weeks ago at one of my favorite cafeterias. I’m not going to mention the establishment, but there is probably one very close to you and the strawberry pie is irresistible.
As a force of habit, I was looking up to see the condition of the diffusers. I typically try to do this after I have eaten. The condition was not good and we noticed something else.
All of the drop-in tiles were bowed downward. With the amount of exhaust ventilation required for an establishment like this, it was obvious that the facility was under negative pressure and the relative humidity was too high.
The negative condition of the facility was pulling in fungus, dirt and mold spores into the room. The tiles were absorbing moisture from the humid air. Visible signs of fungal growth were apparent on many of the tiles. Roof leaks could have contributed to some of these conditions, but the negative pressure of the building was adding to the amount of moisture pulled from the common area above the grid. Not a pretty sight.
Another noticeable problem was the amount of outside air flooding the facility every time the doors opened. Undesirable dirty and humid Houston air entering the building added to the indoor air quality issues. The condition of the return air grills was a good indication of the amount of particulate matter being “sucked” into the structure.
With all of the unfiltered and unconditioned air entering the building under these negative pressure conditions the air quality was definitely being impacted, to the NEGATIVE!
The steps to positively pressurize a building and positively impact indoor air quality are the subject for another article. For now, identifying these problems for your customer is the first step on the path to better indoor air quality for your clients.
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