A fan rating typically refers to the cubic feet of air per minute that the individual unit is capable of moving. This is especially important information when considering exhaust fans for industrial use, which may be dependent upon such ratings for safety and efficiency. Some fans, such as ceiling fans, may also have a fan rating, based on standards such as quality and reliability.
The fan rating rating of cubic feet per minute is often abbreviated to CFM. In some cases, these fans are responsible for removing harmful substances from the air. Therefore, this type of fan rating is very important, especially in those situations where contaminated air may be a big concern, such as hospitals and facilities using potentially dangerous gasses.
There are two main factors that affect the cubic feet per minute rating, size and speed. The rotational speed of the fans can often be adjusted depending on the need. This helps save electricity in those situations when a lower fan speed can be used. The other thing to consider is the size. The blade size is usually expressed in diameter, and will have a big impact on the overall fan rating as bigger blades generally move more air.
Another important consideration, in addition to the cubic feet per minute, is the number of air changes per hour. This rating explains how many times in an hour a complete air change will take place in a room. This is often a very important consideration in airplanes, where keeping fresh air circulating is important for the health and comfort of passengers. In the case of pressurized aircraft, these are very specialized types of fans, but still have some type of rating associated with them that manufacturers depend on.
For ceiling fans and other types of personal use fans, there is a big difference in fan ratings. In these cases, the goal is not necessarily to move a great deal of air in and out of a location, but rather to simply create air circulation in order for people to remain comfortable. While the rating is not as important in residential uses, some retailers have developed their own fan rating system.
The system used by retailers is often based on the quality. For example, one retailer rates fans from performance grade down to an economy grade. The tradeoff for the quality is the discounted cost, which may be attractive to some consumers. There is no industry standard for these types of ratings and they may vary greatly from one retailer to another, if they are available at all.
