CONCORD, N.H. (AP) -New Hampshire has set new standards for outdoor wood boilers, after a growing number of complaints.

A new state law requires homeowners who use boilers that are installed as of this month to consider the distance between the devices and their neighbors. Newer models will also have to meet tightened emission standards starting next year.

The Department of Environmental Services says the state, with the help of municipalities, will also restrict or shut down already-installed boilers if they continue to choke neighbors with black smoke.

More people are using the wood-fired boilers to beat high energy prices. A boiler typically sits in a small shed outside a house. It heats water and carries the energy through pipes to warm the building.

But neighbors say the boilers produce a thick, black smoke that aggravates lung conditions and ruins clothing.

The new law will phase in the tougher standards.

Owners of existing boilers don’t have to move them, but if they are deemed a nuisance or health hazard, the state or community will “abate” the problem or require the boiler be shut down if the problem can’t be remedied, DES said.

A boiler purchased and installed between now and January that doesn’t meet federal emission standards must be no closer than 200 feet from a neighboring building. It must also have a permanent stack at least two feet higher than the peak of roofs of buildings within 300 feet.

As of 2009, any wood boilers sold must meet the federal particulate emission standard and meet the 200-foot distance and 2-foot stack requirements.

By 2010, all units sold must meet the .32 pounds standard and will be able to be installed no closer than 50 feet to a neighboring property line, with the thinking that they will be less polluting.