As with all models, one should be cautious of the assumptions and uncertainties in these air quality models. Given that a model is a simplification of reality, one should expect a reliable range of outcomes, not a definitive outcome at one point in space and time. These air quality models afford policy-makers information about the utility of various policy instruments. The measurements by these monitors serve to describe the ambient air conditions experienced by humans and ecosystems. Further, air quality monitors can be used to calibrate air quality models and to assess the effectiveness of emissions controls.
Government agencies site most air quality monitors in urban areas.
The National Park Service does monitor most national parks, but many rural areas are not monitored. Monitoring can be used to assist federal land managers in the air quality-related values assessment. The managers can determine the present levels of various air pollutants.