New Hampshire air quality today

The New Hampshire Department of Environmental Services forecasts ozone from April through September, and it treats the problem as a regional one. Twelve monitoring stations across the state track ozone. Two of them are photochemical assessment sites, one in Londonderry and one at the summit of Miller State Park in Peterborough, sampling hourly volatile organic compounds — the ingredients rather than the finished product. When NHDES investigated ozone trends in southeastern New Hampshire and the surrounding region, it read those two sites alongside nine more in Maine and Massachusetts.

Keene’s winter is the opposite problem. The city sits in a flat basin ringed by higher ground, where thermal inversions form on cold, still nights and fine particulate from residential woodstoves collects under the lid until the sun breaks it. A changeout program run in 2009 and 2010, paid for with EPA money and funds from a multi-state settlement, took 86 old stoves out of the city and put back 63 newer models, 15 pellet stoves and eight gas appliances. Keene State College has kept a wintertime air quality project going since, with the Southwest Region Planning Commission, the city, Cheshire Medical Center and NHDES; it now places sensors in the homes of citizen scientists.

The forecast season and the wood-smoke season do not overlap. The state’s ozone forecast stops at the end of September, months ahead of the inversions that matter most in a valley town, so the winter numbers on this page arrive from monitors with nothing interpreting them. New Hampshire has no city page here yet, which is a fact about our build order and not about the air.