An employee was investigating a noise in an HVAC duct-system. He located a suspect auxiliary blower unit, deenergized it, and then went to retrieve tools. He returned to the blower after approximately 10 minutes. The fan/belt/pulley were slowly rotating even though power had been isolated. The employee removed a cover so he could press a tool against the belt to bring the blower to a stop. While reaching for the tool, his hand slipped into the pulley/belt resulting in an amputation to the right index finger from the base of the nail to the end of the finger. Also, the top third of the right middle finger was degloved.