Complete the following problem set. Show all of your work in order to receive credit. Write clearly
and neatly. Watch your units and significant figures. Upload spreadsheet(s) .
1) Estimating air change rates and ventilation rates:
In Summer 2020, a research team conducted tracer gas tests in several rooms.
In each test, CO2 was injected from a portable tank to elevate concentrations in the tested room, and then
CO2 concentrations were allowed to decay back towards background levels. We measured CO2
concentrations simultaneously inside the room and outside. The tested rooms were left unoccupied during
the tracer tests. Resulting indoor and outdoor CO2 data from one such test conducted in a room in a room are provided. Using these data(CO2 data), estimate the air change rate in the classroom
under the tested conditions. Show your work, including the graph (or description of any other method) you
used to estimate the AER. Give your answer in units of inverse hours (1/h). Also calculate an effective
outdoor air flow rate (in units of CFM) from these tests assuming the floor area if 576 ft2 and the ceiling
height is 12 feet high.
2) Evaluating air cleaning technologies
The market for air cleaning technologies is booming. Numerous companies are heavily marketing their
various air cleaning technologies for their ability to combat COVID-19 transmission in indoor
environments. The marketing claims are often bold, and typically sound quite promising:
• ABC technology uses reactive molecules [or super oxides or positive and negative ions] to destroy
SARS-CoV-2 on surfaces and in air!
• XYZ technology has just been granted emergency FDA approval!
• DEF technology reduces viable SARS-CoV-2 [or surrogate organism] by 99.99% in 60 minutes!
You have been asked to evaluate the effectiveness of one of these technologies from a company called
Aerus, which recently hired Deborah Birx, the former White House Coronavirus Coordinator in the Trump
administration, to help promote sales of their ActivePure® technology, which purports to kill a variety of
pathogens including SARS-CoV2: https://www.activepure.com/scientific-proof/. The manufacturer’s
sales representative shared you with a compilation of test reports(active pure testing dossier), provided with this
assignment. Using the first report in that packet (I. Aerosol Research and Engineering Laboratories testing
of their Medical Guardian product), translate their MS2 bacteriophage test results from a log-reduction
shown on their website (i.e., 99.9999% reduction after 60 minutes) to an equivalent clean air delivery rate
(CADR). How does this CADR value compare to a typical portable air cleaner with a HEPA filter?
Comment on any strengths and weaknesses of these test reports that you observe.