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Frequently Asked Questions

  1. Can I be alerted when Air Quality is forecast to be poor?
  2. The Air Quality Forecast for a pollutant is different than what the current data shows. Why is that?
  3. Why was Maine broken into the eight Air Quality Forecasting regions?
  4. I live on the border between two (or more) forecast regions. When they have different forecasts, which should I follow?
  5. I don't see information about fine particle monitoring in Aroostook County in Northern Maine on these web pages. How do you know what to forecast for this area?
  6. Does ozone behave differently with height?
  7. I can see pollution in the air, is it ozone?
  8. MEDEP and EPA warn about Ozone yet it has been touted as a great indoor air cleaner. Why is that?

1. Can I be alerted when Air Quality is forecast to be poor?

Yes, you can.  EPA created EnviroFlash an automated zip-code based air quality alert email notification system.  EnviroFlash covers the entire state of Maine and allows the subscriber to decide at which Air Quality Index (AQI) level to receive email notification. 

DEP's Air Quality Meteorologists submit the forecast to EPA's AIRNOW system every day of the year.  EnviroFlash will review the forecast in AIRNOW at 4:00 each afternoon and when tomorrow's forecast in your location matches the criteria you set up an email will be sent to you.  Let EnviroFlash help you 'Keep an eye on the AQI'. 

Go to: http://www.maine.gov/dep/air/ozone/enviroflash.htm for more information about EnviroFlash and how to subscribe then click on the map to initialize the subscription process for EnviroFlash!


2. The Air Quality Forecast for a pollutant is different than what the current data shows. Why is that?

You are viewing the data during a small part of the day, yet values will be higher during another part of the day and that data is what the forecast is based on.

This is often the case with Ozone which is a photochemical pollutant and peaks during the afternoon hours (from April through September). Both morning and evening values are likely to be low. Ozone forecasts are for the highest 8-hour period of the day.

For Particle Pollution values, the running 24-hour average for several hours may be Moderate yet the block 24-hour average from midnight to midnight for that day ends up being Good. It is this block, midnight to midnight, average for which we issue the forecast. When we believe that particle levels will build in late one day and clear out early the next we will mention this in the forecast details on the Air Quality Forecasting web page.

Finally, although we make every effort to forecast as accurately as possible, it is still an inexact science and, just like the weather forecasts upon which we base our Air Quality Forecasts, we may be wrong. Sometimes we know the values will end up near the break point between categories. In those cases we carefully weigh the various factors contributing to the pollution levels and make a decision based on experience and the most likely weather conditions expected. Sometimes we believe it will be such a close call that we err on the side of protecting the public and issue the forecast for the higher of the two categories. Unlike weather forecasters who are able to give a range of temperatures or weather conditions, we issue forecasts for a specific category and a very small change in pollution levels will 'make' or 'break' the forecast.


3. Why was Maine broken into the eight Air Quality Forecasting regions?

For years we had three forecast regions: Coastal, Interior and Northern. As we learned more about how Ozone and Particle Pollution behaved in Maine it became apparent that the three regions were not adequate. They were fairly good for Ozone, but not good at all for Particle Pollution. So we refined and subdivided the former regions using the monitoring data for both pollutants and our best judgement.  We created seven major forecast regions which display in the table as well as on the forecast maps.  This gives us more flexibility in issuing a graphical forecast and better descriptive and consistent regional terms to use in the text and hot line messages. Of course, it also pushes us to do better and refine our forecasting knowledge. Who knows, in the years to come we may realize these seven major regions need to be revised, especially as we learn more about how pollution behaves in our northern areas.  In addition to the seven major forecast regions, we've added a region called 'High Elevation'.  This region includes the ozone monitor on Cadillac Mountain in Acadia National Park.  The High Elevation forecast region only displays in the table because it would have been a tiny dot on the map which would have been hard to display properly.


4. I live on the border between two (or more) forecast regions. When they have different forecasts, which should I follow?

In the atmosphere political boundaries do not exist and neither do forecast regional boundaries. The forecast regional boundaries were positioned based on years of monitoring information and our best judgement. It is a good idea to view the borders as a transition between regions rather than a sharp difference.  If you are sensitive to the pollutant in question and live or expect to be along the border between two differing forecasts assume the higher forecast category from the regions will prevail in your area. This will enable you to take appropriate precautions to safeguard your health. We strive to give you the information you need to protect your health. While the new forecasting regions allow us to issue a forecast that more accurately portrays what we believe will happen, there are more border areas.


5. I don't see information about fine particle monitoring in Aroostook County in Northern Maine on these web pages. How do you know what to forecast for this area?

There is a continuous fine particle monitor run by the Aroostook Band of MicMacs in Presque Isle, Maine.  They display this data at: http://www.micmacenvironmental.com/air/cfm/airdata.cfm .  In addition, this data is submitted to EPA's AIRNOW website.  I can view the data through AIRNOW's technical website for forecasters and monitoring personnel.  The general public can also view current fine particle data in Maine (including the Presque Isle fine particle current value) by going to AIRNOW's local page: http://cfpub.epa.gov/airnow/index.cfm?action=airnow.fcsummary&stateid=23


6. Does ozone behave differently with height?

Yes.  We've studied years of ozone data from the Cadillac Mountain monitor.  We've learned that:

  • Ozone levels do not drop as readily after the sun sets at high elevation sites such as Cadillac.  In fact, Cadillac Mountain's ozone levels frequent peak after 10 PM while low elevation ozone levels are dropping.
  • Cadillac Mountain's height places the monitor at an elevation to monitor ozone transport aloft.  At this level ozone is more stable and doesn't break down as readily.  At this level transport winds have reduced friction from the surface so ozone aloft can travel faster and further than surface ozone.
  • Additionally, Cadillac Mountain is geograhically located downwind of major metropolitan areas and large emission sources that are outside of the state of Maine.  Ozone is formed by chemical reactions in the atmosphere in the presence of sunlight.  So the pollution emitted in one area can be lofted and transported to another with ozone forming as the air mass is transported.

For information on how ozone differs from one part of Maine to another, from one year to another and during the day please use the Air Quality Trends link in the blue column to the left.


7. I can see pollution in the air, is it ozone?

Ozone is a colorless pollutant. You cannot see ozone. You may be looking at fog or mist. If you are seeing pollution in the air, it is particles. Particle pollution affects the lungs and so much more. Check out the Particle Pollution health message by going to: http://www.maine.gov/dep/air/ozone/pm_health.htm. Check out the Ozone health message by going to the following link: http://www.maine.gov/dep/air/ozone/ozone_health.htm.


8. MEDEP and EPA warn about Ozone yet it has been touted as a great indoor air cleaner. Why is that?

Ozone in the lower atmosphere is a pollutant. There is no doubt about that. While ozone is able to clean the air, one needs to monitor its use very closely to avoid unhealthy levels. This is a very complicated process and not easily accomplished without sophisticated monitoring equipment and continuous vigilance.

For an article written about air purifiers, go to: http://www.maine.gov/tools/whatsnew/index.php?topic=IOB&id=796&v=Article

The Maine Indoor Air Quality Council covers general indoor air quality issues at: http://www.miaqc.org/

The U.S EPA deals with indoor air in general at: http://www.epa.gov/iaq/index.html and ozone generators/air purifiers more specifically at: http://www.epa.gov/iaq/pubs/ozonegen.html and http://airnow.gov/index.cfm?action=airnow.DisplayStory&myItemID=1404&StoryType=3
California Air Resources Board has issued a report assessing the health impacts of indoor air pollution. Air 'purifiers' that emit ozone were included in their list of indoor air pollution sources which contribute to asthma, respiratory disease and more. For more information go to: http://www.arb.ca.gov/research/indoor/aircleaners.htm