The most efficient wood stove yet was tested recently by Omni Environmental Services in Portland, Oregon. Designed by former MOTHER EARTH NEWS researcher B.V. Alvarez, the Tech IV by Fisher achieved an overall heating efficiency of 79.5%! The particulate emission rate of Alvarez's fireplace insert amounted to just 2.4 grams per hour, making it one of only seven stoves to qualify for sale in Oregon under that state's particulate emission law. The Tech IV's performance also qualifies it for sale under the more restrictive 1988 standard. The stove is manufactured by Cesco Industries.