sites are, as of November 2010, located in all the major Front
Range cities from Pueblo to Fort Collins and in Greeley, Cortez, Elbert, Grand Junction,
Platteville, and Rifle. There are 19 sites monitoring PM2.5. Of these, eight locations
collect only filter samples, two locations collect only continuous hourly data,
and nine locations collect both filter sample data and continuous hourly data. Ozone
sites are, as of November 2010, located all along the Front Range and in Cortez,
Grand Junction, and Rifle. There are 21 monitoring locations for ozone. All of these
sites are continuous monitors.
Measurement at filter sites:
Clean filters are equilibrated at a known temperature and humidity, precisely weighed
by a microbalance in a laboratory clean-room, shipped to the sites under “chain of custody”
, and sampled for 24 hours
from midnight to midnight. The filters are collected and sent back to the lab, with
associated data, for equilibration and post-weighing analyses. The pre-weight is
subtracted from the post-weight to get a net weight. Sampler data, including the
volume of air that flowed through the filter for 24 hours, is matched to the lab
data using a unique filter ID to get a concentration of the particles in the air.
The mass of particles per volume of air is calculated to get micrograms per cubic
Measurement at continuous monitoring sites:
Continuous air monitors use a variety of methods to measure levels of different
pollutants in the air. They produce measurements every hour of every day. These
measurements are sent by computer to the CDPHE Air Pollution Control Division. You
can view this data
to help you make decisions to reduce your risk of health problems due to air pollution.