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The longer the air ducts, the less efficient the HVAC unit will be. When air travels through long ducts, there’s a higher chance to escape from tiny holes. At the same time, you must make sure they are not branching in a very complex way because air duct cleaning will be harder if they are intersected.

Indoor air quality can be affected by one or more of a few things: The levels of buildup of dirt and obstructive residue in the vents, the condition of the air filter in the system, the levels of dust in the home after any renovations and how adequately the vents and ducts are sealed. If you are unsure, then opting for a licensed industrial hygienist to come and test can help determine if there is a problem.

There are times when you just do not seem to bother to check on your HVAC system. When this happens you are running the risk of dust, dirt, pollutants, allergens and other harmful substances to accumulate in your HVAC system especially in the air ducts, filters and vents. Aside from affecting the efficiency of your heating and cooling units, you are also putting your health in danger.

Heating, ventilation, and air conditioning (HVAC) systems have been shown to act as a collection source for a variety of contaminants that have the potential to affect health, such as mold, fungi, bacteria, and very small particles of dust. 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.

The best way to determine if the HVAC system cleaning was effective is to perform a visual inspection of the system before and after cleaning. If any dust or debris can be seen during the visual inspection, the system should not be considered cleaned. While you can perform your own visual inspection using a flash light and mirror, a professional cleaning contractor should be able to allow you better access to system components and perhaps the use of specialized inspection tools. In addition, following this post-cleaning check list can help to ensure a top quality job.

The amount of time it takes to clean a residential HVAC system depends on many variables such as the size of the home, location of the units, the number of systems, the extent of the contamination and the number of HVAC cleaners performing the job. On average a single system home with two technicians takes between three to four hours to perform a thorough cleaning. On an average two system home with two technicians it can take five to eight hours.

Frequency of cleaning depends on several factors, not the least of which is the preference of the home owner. 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 most effective way to clean air ducts and ventilation systems is to employ Source Removal methods of cleaning. This requires a contractor to place the system under negative pressure, through the use of a specialized, powerful vacuum. 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. The debris can then travel down the ducts to the vacuum, which removes it from the system and the home.

Antimicrobial chemicals are applied by some companies to the interior surface of the air ducts, to treat microbial contamination such as fungi (mold), viruses or bacteria. Before any antimicrobial chemicals are used, the system should be thoroughly cleaned. It is critical that any antimicrobial treatment used in your system be registered by the U.S. Environmental Protection Agency specifically for use in HVAC systems. The use of antimicrobial chemicals is an additional service that is not part of a typical air duct cleaning project.

You should interview as many local contractors as possible. Ask them to come to your home and perform a system inspection and give you a quotation. To narrow down your pool of potential contractors, use the following pre-qualifications:

• Make sure the company is a member in good standing of the National Air Duct Cleaners Association (NADCA).

• See if the company has been in business long enough to have adequate experience.

• 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.

The Environmental Protection Agency says that “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, and level of contamination” and type of duct material.

Consumers should beware of air duct cleaning companies that 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.

(If you have knowledge of a practicing “blow-and-go” air duct cleaner, contact your local Better Business Bureau to report the company, and your local, federal, and state elected officials to demand legislation.)

NADCA does not endorse one kind of equipment over another. There are two main types of vacuum collection devices: (1) those mounted on trucks and trailers, and (2) portable units. Truck/trailer mounted equipment is generally more powerful than portable equipment. However, portable equipment can often be brought directly into a facility, allowing the vacuum source to be located closer to the ductwork. Both types of equipment will clean to NADCA standards.

All vacuum units should be attached to a collection device for safe containment prior to disposal. Any vacuum collection device which exhausts indoors must be HEPA filtered.

A vacuum collection device alone will not get an HVAC system clean. The use of methods and tools designed to agitate debris adhered to the surfaces within the system, in conjunction with the use of the vacuum collection device(s), is required to clean HVAC systems. (For example: brushes, air whips, and “skipper balls.”)

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, for a list of NADCA members near you, click here. 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. ASCSs are also required to further their industry education by attending seminars in order to maintain their NADCA certification status.

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

An enormous waste of energy occurs when cooled air escapes from supply ducts or when hot attic air leaks into return ducts. Recent studies indicate that 10% to 30% of the conditioning air in an average central air conditioning system escapes from the ducts. For central air conditioning to be efficient, ducts must be air tight. Hiring a licensed service technician to detect and correct duct leaks is a good investment, since leaky ducts may be difficult to find without experience and test equipment.

The old standby of duct tape is ineffective for sealing ducts. Obstructions can impair the efficiency of a duct system almost as much as leaks. You should be careful not to obstruct the flow of air from supply or return registers with furniture, drapes, or tightly fitted interior doors. The large temperature difference between attics and dusts make heat conduction through ducts almost as big a problem as air leakage and obstructions. Ducts in attics should be insulated heavily in addition to being made airtight.