Service Area We provide service to all of Howard County. To learn more about our service area or if you don't see your town listed, please call the office at 410.381.7991. Clarksville Columbia Elkridge Ellicott City Fulton Laurel Marriottsville Sykesville West Friendship Woodbine Need HVAC Service? Call the experts at Environmental Systems Associates. Call us at 410-381-7991 Environmental Systems Associates proudly provides HVAC service to Howard County. Visit our service area page for more coverage details, call us at 410-381-7991, or request service online today.