Several rural Minnesota families evacuated their homes last week when the odors from a nearby dairy farm reached unhealthy levels. Hazardous hydrogen sulfide levels at Excel Dairy near Thief River Falls, Minn., in northwest Minnesota triggered state Department of Health toxicologist Rita Messing to advise nearby homeowners to leave their homes. At least a half-dozen families living near the 1,500-cow farm left their homes to stay with relatives or in hotels.