Filters containing a layer of activated carbon were installed in two “experimental” filter banks
in an office building located in Sacramento, CA. The ozone removal performance of the filters
was assessed through periodic measurements of ozone concentrations in the air upstream and
downstream of the filters. For reference, ozone concentrations were also measured upstream
and downstream of a “reference” filter bank containing filters without activated carbon. The
two experimental filter banks treated the air provided to a single building zone while the
reference filter bank treated the air provided to another isolated zone. The carbon-containing
filters selected for study were 5.1 cm thick synthetic-media filters with a particle removal
efficiency rating (ASHRAE, 1999) of MERV 8, with 300 g of activated carbon per 0.09 m2 of
filter face area, and with a cost of $U.S. 29 for a 61 cm by 61 cm filter. The manufacturer’s
reported pressure drops for these filters are 58 and 138 Pa with face velocities of 1.5 and 2.5
m/s, respectively. Although filters with a MERV 8 efficiency are often used as the only filter
in a HVAC system, in this building these carbon-containing filters were used as pre-filters
located immediately upstream of 38 cm deep pleated bag filters with a “dust spot” particle
removal efficiency (ASHRAE, 1992) rating of 85%. The reference filter bank was identical to
the experimental filter banks except that it contained 5.1 cm thick MERV 8 pleated syntheticmedia
pre-filters containing no activated carbon.