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The Smelly Package Unit

This story begins with a teacher who, because of a smell in her classroom, began frequently calling-in sick, complaining of headaches and medical problems.  Her classroom was in a newly built section of the elementary school and it was still very early in the school year.  She openly blamed the air conditioning unit even though substitute teachers in the same classroom did not complain.  The installing HVAC contractor was summoned to the job site  by the school district repeatedly to resolve the problem but could not find anything wrong with the equipment, or his installation.

Elementary school heating and air conditioning has come a long way  since I was a kid.  When I was in school I remember opening the upper set of windows in our classroom with a long wooden pole. Items like this probably aren’t allowed in schools these days because they look too much like a weapon, but back then, it was the only way to get airflow into my elementary school classroom.

The summertime ventilation cycle was simple back then; the teacher would open the door to allow clean fresh air in and a student would be asked to open the upper windows to exhaust the heat built up inside the classroom.  But this article is about a modern elementary school, with a modern problem.

In the field of HVAC, offending odors can be a very difficult problem to solve because it’s subject to personnel perception.  It is not like electrical or refrigeration problems that are commonly solved, since there are no tools in the trade that can measure the intensity or pinpoint the location of odors and smells.

While it is true that a newly built school will have materials that out-gas fumes, she claimed it only happened while the air conditioning was running.  By the time this problem came across my desk, the teacher had made such an uproar that students believed the air conditioning unit was making them sick too.  Now we had the expected over-reaction from parents that were upset and a very displeased school district on top of it.  As the Technical Support Representative for the manufacture of this equipment, I was asked to look into the problem.  I have been on some unusual job site visits in the past, but this visit was heightened because the teacher refused to return to work unless the air conditioning unit was removed and replaced with a new one.

I did not expect the large force of representatives from the school district headquarters that descended on the job site while I came to inspect the unit; the large turnout made the installing contractor very nervous.  Since nobody else had smelled the odor, it was important for me to establish a baseline of what the teacher thought she was smelling.  We all met her in the classroom and I listened to the medical problems the doctors were treating her for and her description of the odor.  I then asked some basic questions like; does it happen in heat or cooling mode?  “During cooling mode” was her response.  This information eliminated the heating cycle and the gas furnace section of the unit.  We started the air conditioning unit and I asked  if the odor was present. “A little bit,” she answered.  I looked for any collaborating responses from the large group assembled in the room;  besides the faint smells of fresh paint and new carpet, nobody else could perceive any usual odors.  She then changed her response and said she doesn’t smell it at that moment.

At that juncture, I started looking for clues in the classroom.  I was searching for any sources of heat that could create a burning smell or odor that would be specific to this classroom. With no obvious source of odors found, we left the teacher and students behind and climbed the access ladder to the roof.  To my surprise, all the representatives from the school district followed me up the ladder.  We hooked up refrigerant gauges to check pressures out of habit.  We also monitored all incoming volts and amps but found nothing abnormal.  We removed all panels to smell each section.  We searched the supply air, return air, and furnace combustion chambers – nothing. We looked for factory faults like fallen insulation, glue, or paint overspray on a motor that would generate a smell – also nothing.   We searched for signs of overheating on the motors, compressor, and heat exchanger that might lead to a smell but found none.  Out of desperation, we took most of the unit apart, but to our dismay, found nothing.

I had to take a step back and reconsider the situation while the contractor reassembled the parts of the unit which lay in pieces on the roof.  If the unit was not generating the smell that caused the teacher to be sick, where was it coming from and what was producing it?  I felt like this packaged air-conditioning unit would be found guilty unless proven innocent.  The school district personal gathered in a private huddle on the other side of the roof forming a plan which I’m sure would not go well for me or the installing contractor.   The pressure to solve problem was on my shoulders now; if I could not find the answer I was sure they would ask for a completely new package unit.  There were also insinuations from the school district personnel that all future contracts for this district would be in jeopardy if this problem wasn’t resolved.

The bell rang at the start of recess and I had been on the roof for almost 2-hours and we were not any closer to solving this problem.  You could hear the happy kids running out into the hallways below, unaware of the drama unfolding on the rooftop above.  I looked around inside the return air section of the unit one last time.

Then it surfaced, a foul smell that was hard to believe, almost enough to knock you off your feet.  My nose was curled but I had to keep sniffing inside the return section to find where it was coming from.  I pulled my nose out of the unit because I could not stand the offensive smell anymore and to my surprise, it was worse outside of the unit.  What was that nasty smell?  It was foul and putrid.  The district personal had caught a whiff on their side of the roof and came rushing over.  We collectively agreed that we had found the awful smell, but needed to find the source.  And then, through watering eyes, we saw it.

The light winds blowing across the roof directed sewer gases from the boys and girls restroom vent pipes toward the package unit’s fresh air intake.  Even thought the vent pipes were beyond the minimum distance required from the unit’s fresh air intake, we suspected that the plumbing contractor might not have properly trapped these pipes.  Even in its minimum position, our package unit’s fresh air intake would pull in this smelly air.

The installing contractor was grateful for the discovery and the crisis was solved and the school district was on the phone with the plumbers before we got off the roof.  Modern schools make every effort to provide proper heating, ventilation, and air conditioning to the occupants in the classroom. And in today’s energy-efficient classrooms, temperature is important but so is ventilation.  Just like when I was growing up, proper ventilation promotes the best learning environment.

About the AuthorTony Albers is a highly successful trainer who has taught heating and air conditioning classes designed specifically to meet the needs of today’s busy technicians and engineers.  For the past 33 years he has worked to advance the field of heating and air conditioning by teaching classes for IHACI, RSES, Southern California Gas Company, and San Diego Gas & Electric.  In the last 23 years he has traveled extensively throughout North America for US Air Conditioning Distributors and Venstar, giving workshops and seminars for large HVAC distributors and manufacturers.  Albers has been on the Continuing Education Committee for the Institute of Heating and Air Conditioning Industries and has written articles for Indoor Comfort News, HVAC Insider, and the Southern California Chapter of ASHRAE.