Good air circulation from properly working air ducts is beneficial for a number of reasons. The forced air system within your home or office is meant to deliver fresh clean temperature controlled air for those within the rooms. If you have been noticing higher than usual energy bills this may be a sign that your air ducts need to be cleaned. The forced air system within your home or office runs on electrical power. The blower forces air into the room through duct work piped into every room. Pushing large volumes of air takes work and this work is provided by the electrical power. If the ducts are dirty and in need of cleaning the amount of energy needed to force the same volume of air into the rooms will increase. 

There is a physical resistance to forcing air through dirty ducts and this resistance needs to be overcome by the motor forcing the air into the rooms. If more force is needed to push the same amount of air as usual this must require more energy. This increased energy is taken from the electrical potential provided and since we pay for electrical energy we therefore end up paying. Another sign that your air ducts need to be clean could be the regulation of temperature within a single or number of rooms. If you find on a particularly cold or hot day the temperature in one area of a room to be adequate but lacking in another nearby area your air ducts may need to be cleaned. Increasing or decreasing the thermostat temperature may cool or heat that area which is lacking but it may also cool or heat the area which was not by uncomfortable levels.

Over time, and with little heat or cooling loss, the temperature a room thermostat is set at will likely be the temperature of the room. If an air duct delivers warm or cool air into a room the temperature of that room without noticeable energy loses will reach some equilibrium point. If though the temperature outside is particularly cold or hot and the room insulation is unable to maintain a set temperature for long then a poorly cleaned air duct may deliver a lower than needed amount of desired temperature air which will only be able to cool or heat a particular area of a room leaving those areas further from a duct to heat or cool undesirably from outside conditions.

A final and important sign you are need of an air duct cleaning service deals with health and cleanliness. A dirty air duct can deposit unwanted dust and dirt into a room and hence into the lungs of people who breathe in that room. If you maybe noticing unwanted dust and dirt accumulation on furniture and items in a room or maybe have been coughing and sneezing more due to an increase in allergens then maybe it is time to have your air ducts cleaned.