In response to complaints about outdoor wood boilers in the early 1990s the Vermont ANR adopted regulations (Section 5-204) that apply to OWBs installed after October 1, 1997. This regulation established set-back and stack height requirements for OWB installations but did not set an emission standard that would reduce the air pollution emissions from these units. Because complaints continued and OWBs have become increasingly popular, causing greater impacts on Vermont's air quality, the ANR adopted amendments to the original regulation that established first a "Phase I" and then a “Phase II” particulate emissions standard for OWBs sold in Vermont. The current regulation also applies to outdoor pellet-fired boilers. The Phase II particulate standard, effective on March, 31, 2010, promotes the sale and installation of much more efficient and cleaner wood burning technologies in Vermont.
A link to the current Phase II regulation is listed below.