def METHOD_NAME(self, index):
    if (index == 1):
        direction_file = 'fan40_direction'
    elif (index == 2):
        direction_file = 'fan50_direction'
    else:
        logging.error("Invalid PSU number:", index)
        return None
    direction = self.get_attr_value(self.HWMON_PATH + direction_file)
    direction = direction.rstrip()
    """
    1: FB 2: BF
    Since the fan is at rear of the switch, FB means Exhaust; BF means Intake
    """
    if direction == '2':
        return "INTAKE"
    else:
        return "EXHAUST"