Heating, ventilation, and air conditioning (HVAC) systems have been shown to act as a collection source for a variety of contaminants such as; mold, fungi, bacteria, and very small particles of dust. All of these have the potential to affect health. The removal of such contaminants from the HVAC system and home should be considered as one component in an overall plan to improve indoor air quality.

Research by the U.S. EPA has demonstrated that removing debris from sensitive mechanical components within your HVAC system, may allow the system to run more efficiently. Clean, efficient systems are less likely to break down, have a longer life span, and generally operate more effectively than dirty systems.

Source Removal methods of cleaning have proven the most effective way to clean air ducts and ventilation systems. With the use of a specialized, powerful vacuum the contractor places your system under negative pressure. While the vacuum draws air through the system, devices are inserted into the ducts to dislodge any debris that might be stuck to interior surfaces. Any debris can then travel down the ducts to the vacuum, which removes it from the system and the home.

The technique and procedure used for the cleaning is far more important than the type of equipment used. Most types of equipment are capable of effectively cleaning your ductwork as long as proper procedures are followed. The following is a basic explanation of the different types of equipment commonly used for air duct cleaning:
• Truck Mount: A truck mounted vacuum is run from a large truck. A hose is run from the truck into the house so material is drawn outside and into the truck.
• Electric Portable: Portable electric vacuums are special HEPA filtered collection devices that can be used indoors. The vacuum can be set up near the furnace or other connection point so suction is not lost. These vacuums are also ideal for homes or buildings presenting difficult access, or for high-rise apartments and condominiums.

If you want to clean ductwork properly, you have to be able to access the inside of it to do that. Cutting an access hole to attach the vacuum hose then working everything to that one connection point is more efficient than going from vent to vent with the vacuum hose. That method will not get all the debris, and may stir up irritants that could come back into your home when the system is turned back on. Any access opening made in your ductwork should be sealed in a manner that returns the ductwork to the same or better condition.
What are sanitizers, and why would they need to be used?

Sanitizers are anti-microbial chemicals applied to the interior surface of the air ducts, designed to control microbial contamination. It is not uncommon for mold, fungus or bacteria to be present in ductwork. It is a dark, confined space, and moisture can be present, which may create an ideal breeding ground. However, most spores can be removed with a thorough cleaning.

As a "cleaning" company, it is the job of your technician(s) to leave your home in as good as or better condition than when they arrived. Drop clothes may be used if hoses need to be laid on carpeting. Any large collection vacuum used inside your home should have appropriate filtration so as not to allow debris back into your indoor air. Certainly, there may be some debris that falls loose when a vent cover is removed, or when dust is disturbed on the top of exposed ductwork. But your service technicians should take the time for a "general clean up" upon completion of the duct cleaning.

Even though much of the equipment is usually outdoors, the motors of the vacuum and compressor may be heard quite clearly. You probably don't want to schedule your cleaning while the baby is taking a nap, and you might even want to take the baby for a stroll during the louder parts of the procedure. You may want to give special consideration to small children or pets affected by loud noises.

Frequency of cleaning depends on several factors. Some of the things that may lead a home owner to consider more frequent cleaning include:
• Smokers in the household.
• Pets that shed high amounts of hair and dander.
• Water contamination or damage to the home or HVAC system.
• Residents with allergies or asthma who might benefit from a reduction in the amount of indoor air pollutants in the home’s HVAC system.
• After home renovations or remodeling.
• Prior to occupancy of a new home.

The amount of time it takes to clean a residential HVAC system depends on many variables such as the size of the home, the number of systems, the extent of the contamination and the number of HVAC cleaners performing the job. A home with more than one furnace may take several hours or the better part of a day, whereas a single furnace home may take only two or three hours with well-trained technicians and the right equipment. You should ask how long it will take.

Duct cleaning services typically – but not always – range in cost from $450 to $1000 per heating and cooling system, depending on the services offered, the size of the system to be cleaned, system accessibility, climactic region, level of contamination and type of duct material.

Consumers should beware of air duct cleaning companies making sweeping claims about the health benefits of duct cleaning – such claims are unsubstantiated. Consumers should also beware of “blow-and-go” air duct cleaning companies. These companies often charge a nominal fee and do a poor job of cleaning the heating and cooling system. These companies may also persuade the consumer into unneeded services with and/or without their permission.

• Make sure the company is a member in good standing of the National Air Duct Cleaners Association (NADCA).
• Get proof that the company is properly licensed and adequately insured.
• Verify that the company is certified by NADCA to perform HVAC system cleaning.
• Make sure that the company is going to clean and visually inspect all of the air ducts and related system components.
• Avoid advertisements for "$99 whole house specials" and other sales gimmicks.
• Ask if the company has the right equipment to effectively perform cleaning, and if the company has done work in homes similar to yours. Get references from neighbors if possible.

NADCA Members have signed a Code of Ethics stating they will do everything possible to protect the consumer, and follow NADCA Standards for cleaning to the best of their ability. Air duct cleaning companies must meet stringent requirements to become a NADCA Member. Among those requirements, all NADCA Members must have certified Air System Cleaning Specialists (ASCS) on staff, who have taken and passed the NADCA Certification Examination. Passing the exam demonstrates extensive knowledge in HVAC design and cleaning methodologies. ASCS's are also required to further their industry education by attending seminars in order to maintain their NADCA certification status.