Interagency Monitoring of Protected Visual Environments

Nothing can ruin a visitor’s experience of a national park more than a blanket of haze. Not only does air pollution spoil the views that people travel hundreds or even thousands of miles to see, it also disrupts the natural environments that national parks and monuments were designed to preserve, while causing and contributing to a host of health problems for humans and wildlife alike.

Image: left photo of clear air quality next to right photo of hazy air quality at Denali National Park.
Clear visibility of Denali National Park on the left versus the visible haze of Denali on the right.

Since 1985, the AQRC has played a key role in IMPROVE, a program that addresses visibility degradation issues at Class 1 areas throughout the United States: national parks, wilderness areas, wildlife refuges and Native American lands that have been designated by Congress as places to be afforded the highest level of air quality protection under the law.

Spearheaded by the EPA and governed by a steering committee of representatives from federal, state and regional organizations, the Interagency Monitoring of Protected Visual Environments (IMPROVE) program monitors visibility conditions, tracks changes in visibility, and works to identify sources and causes of regional haze at all Class 1 areas, from Everglades National Park in Florida to the Simeon of Wilderness in Alaska.

AQRC oversees operation of all IMPROVE monitoring sites—about 160 locations and counting—where sampling stations designed and installed by AQRC researchers and staff are programmed to automatically collect samples of haze-forming particles from the air on an ongoing basis. Local operators change the stations’ particle-laden filter cassettes weekly and ship them back to AQRC, where most of the analyses to characterize composition and sizes of the captured particles are performed. Tests include X-ray fluorescence (XRF) to determine the composition of elements, gravimetric mass measurements, and optical absorption.

The AQRC group also coordinates carbon and ion analyses that are conducted on the samples at other labs; validates the results; and integrates the different data streams into a unified database.

Comprehensive IMPROVE website

For comprehensive information about the IMPROVE program, including news and data advisories, go to the program's website at

Further Inquiries

Please direct your inquiries related to IMPROVE to Dr. Nicole Hyslop