February - March 2008
got bugs? nuke'em
Turning Up the Heat for Hospitality
By Randy Herold, ENPRO Environmental
The
telephone call came just after Thanksgiving.
The director of housekeeping for the Four Seasons Resort Maui at Wailea wanted to know more about the disinfecting and sanitizing of guest rooms using heat. The Four Seasons is Hawaii’s only five star hotel.
Would it be effective against unwanted critters and mold?
The hotel was undergoing a major renovation of guestrooms and it would be an opportune time to find out.
ENPRO Environmental signed on to conduct a third party evaluation, Precision Environmental, holder of the patent for ThermaPure®, agreed to conduct the heat treatment, and Four Seasons Resort volunteered the guestroom.
Background
In the 1860s, Louis Pasteur brought to the world, pasteurization, a heat process to kill microorganisms. Today, another heat technology, ThermaPure® is used in buildings to kill insects, mold, bacteria, and viruses. It also has the added benefits of structural drying, odor reduction and the elimination of volatile organic compounds. Heat is a more effective and healthier alternative to chemical application.
The ThermaPure® process combines the injection of clean, dry, odorless heat with aerosolization and filtration.
Temperatures in the range of 145º F to 155° F for a duration of two hours prove fatal to the typical organisms that inhabit our living spaces.
The equipment used in heat treatment is relatively simple: portable heaters, air scrubber, air movers, digital thermometers, and thermal imaging cameras.
It’s Showtime
Five commercial grade air movers, three in the bedroom, one in the hallway and one in the bathroom were installed in guestroom 437. Polyethylene sheeting was used as a critical barrier covering the common doorway to the adjacent guestroom. To exhaust the introduced heated air, a negative air machine/air scrubber was positioned in the sliding glass door of the bedroom, and the remainder of the opening sealed with poly sheeting.
Twin propane tanks were positioned in a stairwell across the hallway and connected via a supply hose to the five hundred thousand btu propane heater. From the heater, flexible, Mylar® ducting was attached to the critical barrier covering the entrance door. All of the heat treatment equipment was in place.
Thirteen digital temperature/humidity probes were strategically placed throughout guestroom 437. In the adjacent guestroom, a laptop computer was set up to record temperature and humidity on a real time basis. Ambient air particle measurements were collected from inside the guestroom and compared to outside readings every hour during treatment. Periodic thermal imaging of interior surfaces served to identify any hot or cold spots as the process progressed.
With all equipment staged, pre-treatment biological samples were then collected. Viable fungal growth on the air handler unit (AHU) in the ceiling plenum in the closet, on top of the bathroom door, and from the bathtub rim, were sampled using agar, contact plates.
Viable
bacterial growth on the toilet bowl rim, on top of the vanity counter,
and from bathtub rim, was also sampled. Spore trap samples draw air across
an adhesive trapping airborne particulates including fungi, pollen, insect
parts, mites, epithelial cells, fiberglass, and carbonaceous debris. Culturable
fungi samples were collected from the bedroom by impacting air directly
onto malt extract agar media plate.
To document the efficacy of the heat process to sterilize microbes, six swabs inoculated with Esherichia coli bacteria were placed within the guestroom and six similar swabs were placed outside the guestroom.
Similarly, live, caged crickets, twelve inside the guestroom and twelve placed on the lanai were used to demonstrate insect kill efficiency.
Show Me the Heat
The propane heater was turned on at 1:30 p.m. and the room allowed to slowly warm.
Once the temperature goal had been achieved at 4 p.m., the heater and air movers were turned off. The guestroom was then cleaned, post-treatment biological samples collected and the equipment removed.
Fungal and Bacterial Analytical Results
E. coli
All six swabs inoculated with Eschericia coli located outside the guestroom
maintained viability. Four of the six swabs located inside the guestroom
were sterilized.
Crickets
All crickets placed within the guestroom died as a result of the heat
treatment. All crickets placed outside on the lanai survived.
Interpreting The Results
The concentrations of fungi and bacteria in the guestroom prior to treatment were unremarkable, i.e., there was no known source of contamination of microorganisms and none was discovered by sampling and analysis. Nonetheless, the concentrations of fungi and bacteria in samples collected from the ambient air and surfaces were substantially reduced by the heat treatment process.
The swabs of Eshericia coli located within the guestroom were sterilized
except for two swabs, one located on the concrete floor in the toilet
room and one located on the concrete floor in the closet. The lethal temperature
for Eschericia coli bacteria is typically 140º F for a duration of
24 minutes. Therefore, it is likely these two locations represented cold
spots that did not reach the lethal temperature for the necessary time
period.
The quick thermal death of the crickets suggests that crickets do not
withstand heat .
Randy Herold is president of ENPRO Environmental, a national environmental consulting firm. He is a national board member of the Indoor Air Quality Association and the American Indoor Air Quality Council. A recognized lecturer and expert consultant, he can be reached at rherold@enproenvironmental.com.
