2011
Daily Air Quality Index
2011 Levels At-A-Glance
Number of Good Days
Number of Moderate Days
Number of Days Unhealthy for Sensitive Groups
CARBON MONOXIDE (CO)
OZONE
CO levels in Fort Collins
are significantly
better than the
national air quality
standard, and have
been steadily
improving for the last
20 years. CO is
emitted mainly by
motor vehicles and the
improvement is largely
due to the federal new car emission standards.
Daily readings do not total 365 days due to
monitor down time.
The ozone level at
the Fort Collins
West monitoring
site was worse
than the national
air quality
standard on 8 days
in 2011, with the
highest reading of 86
(parts per billion)
compared with the 75 ppb
standard. The
U.S. Environmental Protection Agency has
directed that the ozone problem be solved
regionally in an area extending to Denver and
Greeley. Ozone is formed when hydrocarbons
and nitrogen oxides react in sunlight. They’re
emitted mainly by motor vehicles and industrial
sources. Daily readings do not total 365 days
due to monitor down time.
362
0
0
PARTICULATE MATTER
(PM10 AND PM2.5)
PM10 (particulate matter smaller than 10
micrometers in diameter)
measured better than the
national health standard
throughout 2011. These
particles come
from roads,
fields, and construction
sites. Daily readings do
not total 365 due to
monitor down time.
351
0
PM10
338
6
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78
8
0 Extremely Poor Days
36 Poor Days
0
Fine particles or
PM2.5 (particulate
matter smaller than
2.5 micrometers in
diameter) measured
slightly better than
the national air quality
standard on the highest
day. PM2.5 comes from
the incomplete
PM2.5
combustion of motor
vehicle fuels and from
reactions that occur
between certain pollutants in
the
atmosphere. Fine particles
are small enough to bypass the lungs’ natural
defenses and can be deposited in the lungs.
In addition, PM2.5 is the principle factor
in poor visibility.
0
277
VISIBILITY
124
Good Days
102
Missing
Data
Days
103
Fair Days
Visibility is a measure of how clear the air looks.
Note that the Colorado visibility standard is
based on observer preference or aesthetics
rather than health impact. Although visibility
on the highest day in 2011 was almost two times
its preference limit, the fine particles mostly
responsible for the brown cloud consistently
measured better than the PM2.5 limit based on
health. To distinguish visibility from the healthrelated pollutants, it is reported on a separate
Visibility Standard Index with categories good,
fair, poor, extremely poor, and “missing.” Missing
data occur on days when high humidity interferes
with visibility measurements.
Air Quality
fcgov.com/airquality
970-221-6600
2011
This photo is barely in the “poor” visual
category.
Excellent visibility.
100%
VISIBILITY
Fort Collins visibility remains consistently worse than the
Colorado standard an average of one day out of four.
Not in Compliance
90%
In Compliance
PERCENT OF DAYS
80%
70%
60%
50%
40%
30%
20%
10%
2002
2003
OZONE
0%
50%
40%
30%
20%
10%
2010
2008
2006
2004
2002
2000
2011
2010
2009
2008
2007
2006
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
0%
2005
10%
60%
2004
20%
70%
2003
30%
80%
2002
40%
90%
2001
50%
2011
100%
2000
60%
2010
For 12 years, PM2.5 has consistantly measured
around 80% of the current health standard.
1999
70%
PERCENT OF NAT’L STANDARD
80%
2009
PM2.5
For 20 years, PM10 has remained at roughly half the
health standard with no upward or downward trend.
90%
2008
1998
1980
2011
2010
2009
2008
2007
2006
2005
2004
2003
2002
0%
1996
50%
PM10
100%
2007
PERCENT OF NAT’L STANDARD
100%
FC WEST MONITOR
2001
1996
0%
DOWNTOWN MONITOR
2000
20%
150%
1999
40%
200%
1998
60%
2006
The CO level steadily has decreased due to
vehicle emission standards and vehicle emission
testing.
250%
PERCENT OF NAT’L STANDARD
80%
1997
100%
2005
CARBON MONOXIDE
For 30 years, ozone levels at the Downtown site have
been essentially flat. However, levels violate the
health standard at our second site, Fort Collins West,
which has operated for six years.
120%
2004
1994
2001
1992
2000
1990
1999
1988
1998
1986
1997
1984
1996
1982
1995
PERCENT OF NAT’L STANDARD
1994