Diamond Certified Companies are Rated Highest in Quality and Helpful Expertise.

  • Why this rating is the most accurate.
  • Our editors gather deep company info.
  • Performance is Guaranteed.

Diamond certified companies are top rated and guaranteed

Why Trust Diamond Certified Air Duct Cleaning Companies Rated Highest in Quality?

An air duct cleaning contractor removes dust and debris.

You are the customer. If your goal is to choose an air duct cleaning company that will deliver high customer satisfaction and quality, you’ll feel confident in choosing a Diamond Certified air duct cleaning contractor. Each has been rated Highest in Quality in the most accurate ratings process anywhere. And you’re always backed by the Diamond Certified Performance Guarantee. Here’s why the Diamond Certified ratings and certification process will help you find a top-rated air duct cleaning company and is unparalleled in its accuracy, rigor and usefulness:

1) Accuracy: All research is performed by live telephone interviews that verify only real customers are surveyed, so you’ll never be fooled by fake reviews.

2) Statistical Reliability: A large random sample of past customers is surveyed on an ongoing basis so the research results you see truly reflect a Diamond Certified company’s top-rated status.

3) Full Disclosure: By clicking the name of a company above you’ll see the exact rating results in charts and read verbatim survey responses as well as researched articles on each qualified company.

4) Guaranteed: Your purchase is backed up with mediation and the Diamond Certified Performance Guarantee, so you can choose with confidence.

Click on the name of a Diamond Certified company above to read ratings results, researched articles and verbatim customer survey responses to help you make an informed decision.

More than 200,000 customers of local companies have been interviewed in live telephone calls, and only companies that score Highest in Quality in customer satisfaction–a 90+ on a 100 scale–as well as pass all of the credential-based ratings earn Diamond Certified. By requiring such a high score to qualify, the Diamond Certified program eliminates mediocre and poorly performing companies. Read detailed information about the ratings and certification process.

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DIAMOND CERTIFIED EXPERT CONTRIBUTORS IN THE San Mateo County – Air Duct Cleaning CATEGORY

Ron Frediani is the second-generation owner of AWC, a Diamond Certified company. He can be reached at (650) 273-5410 or by email.

Ron Frediani

diamond certified contributor profile and expert article

Ron Frediani: Capable Expansion

By James Florence, Diamond Certified Resource Reporter

MILLBRAE — As second-generation owner of AWC, Ron Frediani hasn’t just maintained his family’s company—he has also managed to expand upon its capabilities. “My dad and uncle started AWC in 1946 and I started working for them in 1965,” he remembers. “Over time, we’ve branched out from mainly doing window cleaning to providing services like gutter cleaning and power washing. About 12 years ago, we added air duct cleaning to our repertoire. Not only that, the company is now in its third generation with my son, Joe, who will take over when I retire.”

Today, after more than 50 years with the company, Ron says his favorite part of his job is interacting with customers. “For many years, I was out in the field doing the work, so I appreciate the fact that I’m now able to focus solely on dealing with customers. This allows me to put all my energy into making sure we’re providing great service and keeping our customers satisfied.”

A resident of San Mateo County (where he lives with his wife, Carol), Ron spends much of his time outside of work volunteering in his local community. “I’m a longtime Lions Club member, and I previously served as president of our local chapter,” he explains. “I do a lot of community service through the club and help oversee a lot of our projects. One of our big programs right now is providing free eye exams for local children.” When he’s not busy serving his community, Ron likes to relax by watching sports and taking the occasional trip to Hawaii.

In his life and career, Ron espouses the importance of the family dynamic. “We try to treat our customers like we would treat our family and friends,” he affirms. “I think the family dynamic has always been the greatest aspect of our business. Since we’re a family-run business, we get to know our customers and they get to know us.”

When asked what his future retirement will look like, Ron says his life won’t change too much. “I’m the kind of guy who needs to stay busy, so I’ll probably keep doing a lot of the same things I do now. Wherever I am, I like to be active and involved with whatever is going on around me.”

Ask Me Anything!

Q: What are your favorite sports teams?
A: The Golden State Warriors and the San Francisco Giants.

Q: Did you play any sports in high school?
A: I played basketball and baseball.

Q: What’s your favorite thing to do on a rainy day?
A: Relax and listen to music.

Q: What kind of music do you like?
A: I’m a ’50s guy, so I enjoy Elvis, Little Richard and other artists from that era.

Q: What’s your favorite snack?
A: Popcorn.

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3 Ventilation Tips for Homeowners

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MILLBRAE — When it comes to in-home ventilation, there are some crucial aspects all homeowners should know about. Here are three tips to keep in mind: Change your furnace filter. In order to maintain proper ventilation for your home and HVAC… Read more

Expert Video Tip

Video: Furnace Filter Replacement

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Complete Video Transcription:

MILLBRAE — Host, Sarah Rutan: Most people know it’s important to replace their furnace filters, but not everyone knows how often it should be done. To learn… Read more

SELECTED PHOTOS FROM THESE TOP RATED COMPANIES

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INDUSTRY INFORMATION AND RESEARCHED ARTICLES BY THE DIAMOND CERTIFIED RESOURCE

  • Carrier

  • Rheem

  • Trane

  • Rotobrush

  • Sorbo

  • Kohler

  • Moen

  • Delta

  • Grohe

heating ducts
HVAC air ducts
commercial air ducts
residential air ducts (home air ducts)
dryer vents
air vent ducts
air conditioning ducts

microbial decontamination
electrostatic air filter installation
air duct maintenance
biocide application
air duct mold removal
air duct inspection
air duct decontamination
Rotobrush cleaning services
air duct filtration system installation
ductwork vacuuming

Atherton
Belmont
Brisbane
Broadmoor Village
Burlingame
Colma
Daly City
East Palo Alto
El Granada
Emerald Hills
Foster City
Half Moon Bay
Hillsborough
La Honda
Loma Mar
Menlo Park
Millbrae
Montara
Moss Beach
Pacifica
Palomar Park
Pescadero
Portola Valley
Princeton by the Sea
Redwood City
San Bruno
San Carlos
San Gregorio
San Mateo
Sharp Park
South SF
West Menlo Park
Woodside

94002
94005
94010
94011
94014
94015
94016
94017
94018
94019
94020
94021
94025
94026
94027
94028
94030
94037
94038
94044
94060
94061
94062
94063
94064
94065
94066
94070
94074
94080
94083
94096
94098
94128
94401
94402
94403
94404

Bay Area SMACNA (www.bayareasmacna.org/)
Contractors State License Board (CSLB) (www.cslb.ca.gov/)
Environmental Protection Agency (EPA) (epa.gov/)

National Air Duct Cleaners Association (NADCA) (www.nadca.com)
North American Insulation Manufacturers Association (NAIMA) (www.naima.org)
Sheet Metal and Air Conditioning Contractors’ National Association (SMACNA) (www.smacna.org/)

Know What You Want
When You Consider Hiring an Air Duct Cleaning Service

Figure out where you stand and what you want before hiring an air duct cleaning service. You need to know how much you expect from the cleaning and what degree of training you want. No matter where you are looking in San Mateo County, whether in South San Francisco, Daly City, Redwood City, San Bruno, or San Mateo, you want to know what you are looking for. Going into the search, there are a few things to think about. Asking yourself the following questions may help you prepare to hire the best air duct cleaner.

  1. Do I want a Diamond Certified company that is rated best in quality and backed by the Diamond Certified Guarantee?
  2. Do I want chemicals used in my air duct cleaning?
  3. Do I want a firm that will protect my family, my house, and my pets during the cleaning process?
  4. Am I looking for a company that will promise the world or one that will offer a realistic assessment of my house and needs?
  5. Do I want to make sure my air duct cleaning company is licensed as an HVAC contractor?
  6. Do I see mold on my ductwork or smell a moldy smell?
  7. Can I easily access my heating/cooling system components or will I expect the air duct cleaning team to have to create access?
  8. What are my ducts made of? Sheet metal or sheet metal lined with fiberglass? Flexduct? Fiberglass board?
  9. Is it important to me that my air duct cleaner be associated with NADCA?
  10. Is my heating/cooling system working properly before the cleaning?
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What To Ask In Person
Asking Your San Mateo County Air Duct Cleaner Questions in Person

For the most part, customers meet their San Mateo County air duct cleaning company in person during a visit for estimating. A visual estimate is the best way for the company to know what is actually involved with your home.

Some companies may have you describe your system over the phone, in which case, the more you know about it, the better.

But speaking in person with someone who will perform the estimate for your house is one of the best ways to get insight into the process.

  1. Do you see fiberglass used in my heating/cooling system? How will you clean it?
  2. Do you see any places where you may have to open up access to my ductwork or heating/cooling system?
  3. If you do need to open access points, how will you make sure they are sealed after the cleaning?
  4. How many workers do you think the job will take?
  5. How long do you think the job will take?
  6. Will you use vacuum cleaners in the house that don’t vent outside? If so, are they HEPA filtered?

 

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  • What To Ask References
    Hear About Customers' Experiences with Local Air Duct Cleaning Companies

    It’s best to choose a Diamond Certified air duct cleaner because all certified companies have passed an in-depth ratings process that most other companies can’t pass. If you want quality from an air duct cleaner in San Mateo County and the greater Bay Area, you can have confidence choosing a Diamond Certified company. Diamond Certified reports are available online for all certified companies. And you’ll never be fooled by fake reviews. That’s because all research is performed in live telephone interviews of actual customers.

    If you do call references on your own, specifically ask for a list of the company’s 10 most recent customers. This will help avoid them giving you the names of only customers they know were satisfied.

    1. Did you get a written estimate?
    2. Was the quoted price what you paid? Or did they tack on fees for air duct cleaning, air duct vacuuming or air duct sanitizing?
    3. Was your entire system cleaned or did they just blow some air through the ducts only?
    4. Was the air duct cleaning crew pleasant and easy to work with?
    5. Did the air duct cleaning team help you inspect the work after they cleaned?
    6. Were you satisfied with the air duct cleaning provided? Why or why not?
    7. Did the cleaners respect your house and leave it clean after the air duct cleaning was completed?
    8. Was there any damage to your heating/cooling system as a result of the air duct cleaning?
    9. Did you have any chemicals applied to clean your system?
    10. Did the air duct cleaning company recommend any chemicals for killing mold and bacteria?
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  • Review Your Options
    Find and Hire a Good Air Duct Cleaner in San Mateo County

    The Diamond Certified symbol has been awarded to companies that scored Highest in Quality in an accurate ratings process.

    Consider the following questions before deciding on the best air duct cleaning in San Mateo County for you:

    1. Does the air duct cleaning company have the appropriate equipment to perform the job safely, especially HEPA filters on any vacuums that exhaust into the building?
    2. Does the air duct cleaning company ask the right questions about the composition of your duct system and explain how they will handle fiberglass materials?
    3. Does the air duct cleaning company recommend the use of chemicals? If so, can they clearly explain the value of doing so?
    4. Does the air duct cleaning company help you inspect the job after it is complete?
    5. Is the air duct cleaning company licensed and affiliated with NADCA?
    6. Is the air duct cleaning company dedicated to do a complete job, cleaning all components of the system or are they just going to blow some air through just the ducts?
    7. Is the air duct cleaning company acting professionally, giving a valid, written estimate of the cost of the job?
    8. Are the technicians performing the job certified by NADCA?
    9. Does the air duct cleaning company act in accordance with the best ethics, reviewing the site for possible asbestos?
    10. Is the air duct cleaning company concerned with keeping your family, pets, and house safe during and after the cleaning?
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  • How To Work With
    Now That You're Ready to Hire the Air Duct Cleaning Company

    Do a little preparation before you hire a San Mateo County air duct cleaning company, whether you are looking in South San Francisco, Daly City, San Bruno, Redwood City, or San Mateo. Make sure you know what type of heating or cooling system you use. Is it a furnace and air conditioner or do you use a heat pump? What is your ductwork made of? Bare metal pipes? Or are the pipes lined with fiberglass? Does your system also include fiberglass duct board or flexduct? If you cannot tell, ask for help. See if you can find areas where there are large amounts of dirt that may clog the system, look for signs of mold, and look for signs of animal or insect infestation. Consider access to your system – make sure the cleaners can get to it. Be aware of areas where the air duct cleaners may have to create access.

    Working With Your San Mateo County Air Duct Cleaner

    Ask for a written estimate as one of the first steps for working with your air duct cleaning company, whether you looking for help in Daly City, San Mateo, San Bruno, Redwood City, or South San Francisco. Ask any questions you have about how they will clean your heating/cooling system, including whether their cleaning methods are all tools-based or whether they will also use chemicals to clean. Ask to see the labels of any chemicals the company proposes using and make sure the chemical is to be used for the purpose and in the manner described on the label. Work with your air duct cleaner to protect your furniture and floors, as agreed. If chemicals are used, it’s wisest to clear all occupants of the house, including pets, during the application.

    Make Yours one of Your San Mateo County Air Duct Cleaning Company’s Easy Jobs
    The more familiar you are with your air ducts and heating/cooling system, the more you will be able to work with your air duct company. Know the materials used in your system so you can make the appropriate decision. Knowing that you have fiberglass material, for example, will let you know that you cannot clean mold from it but must replace it. Decide with the air duct cleaning company who is responsible for covering and protecting the furniture and floors. If you agree to do any of the protective work, do your part. Speak with your air duct cleaning representative about where new access might be needed. Be clear that you expect any additional access to be sealed after the cleaning. Clarity about expectations prevents frustration on both sides.

    Make sure the air duct cleaning company can contact you for any questions if you are not on site. Let the air duct cleaning company know at the start of the appointment that you would like to use their inspection tools to check after the cleaning is done.

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  • Be a Good Customer
    How Can You Be a Good San Mateo Air Duct Cleaner Customer?

    It's the air duct cleaner’s responsibility to perform quality cleaning on your air duct system. But you play a big part in the success of your air duct cleaner, too. Here are a few simple steps you can take to be a good customer when hiring a San Mateo County air duct cleaner.

    • Be clear and upfront with the air duct cleaner. Let them know what you want from your air duct cleaning, the long-term outcome you’re expecting and specific ways they can satisfy your expectations.
    • Remember, a friendly smile goes a long way, especially when conflict or disagreements happen.
    • Before you hire an air duct cleaner in San Mateo County, restate your expectations and goals, and reiterate to the air duct cleaning representative your understanding of the agreement. Most problems with local aid duct cleaners occur because of a breakdown in communication. By being clear about your expectations and theirs, you can avoid most conflicts.
    • Ask your air duct cleaner if you should call to check on the progress or if he will call you with updates.
    • Be sure your service representative has a phone number where they can reach you at all times while they’re cleaning your air ducts. The work will move along more smoothly if your air duct cleaner can reach you for any necessary updates, questions or work authorizations.
    • When your contractor contacts you, return calls promptly to keep the air duct cleaning on schedule.
    • Pay for the air duct cleaning services right away.

    Why would you want to be a good customer? Air duct cleaners in San Mateo County appreciate customers who are straightforward, honest and easy to work with. Your good customer behavior sets the tone from your end and creates an environment conducive to a good relationship. Things may very well go smoother and any problems may be more easily resolved.

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Check The Work
How Can I Tell If My San Mateo County Air Duct Cleaner Did a Proper Job?

Check the service from your San Mateo County air duct cleaning company, whether in South San Francisco, Daly City, San Bruno, Redwood City, or San Mateo, by visually inspecting the heating/cooling system. Look for dust or particles. A good air duct cleaning company will frequently lend you the same tools they use to inspect, so that you can see the job is well done. Make sure there are no rip or tears if your ducts include fiberglass board, flexduct, or metal pipes lined with fiberglass. Look for mold or mold stains. Mold should be cleaned from metal pipes, and fiberglass material that had mold should be removed.

Check every component of the system. These include the registers, the plenums, the blower motor, and the evaporator coil. Ask the air duct cleaning company if each component on your list has been cleaned, and ask for explanations if they have not. Shine a flashlight on the evaporator coil. You should see the light shine through to the other side. If the air duct cleaner had to make any access openings, make sure they are proper sealed. Test that the system works after the cleaning – in both heating and cooling modes, if you have both.

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Written Warranties
Asking for Warranties on Air Duct Cleaning Services

Your main goal is to ensure that the entire system is cleaned, not just some ducts. You may have prepared your personal checklist of the pieces to be cleaned. Try to get this checklist verified as part of the invoice. If not, go through the checklist to make sure all the pieces of the system were cleaned as you anticipated.

Be sure to ask your air duct cleaning company about warranties. Many provide services with a guarantee of customer satisfaction. Ask what the warranty covers and what the process is for making a claim against the warranty. Ask about the procedure for compensation if the heating/cooling system is damaged during cleaning.

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Top 10 Requests
Popular San Mateo County Air Duct Cleaning Services

Air duct cleaning should be performed by professionals ready to do the full job. You need to make sure that all the components of your heating and cooling system are cleaned properly.

These are not necessarily separate service requests, but points that should be covered by any proper air duct cleaning service as part of the standard air duct cleaning.

Clean and Reset System Components
There are supply registers, return air grilles, and diffusers that are spread throughout your house as part of the heating and cooling system. These should all be removed, cleaned, and returned to their places during the air duct cleaning.

Clean Plenums
The plenums are boxes that attach the devices that heat or cool the air to the rest of the ductwork that spreads through the house. Both the return and supply air plenums need to be cleaned, and you should make sure the supply plenum in particular does not have moisture built up.

Seal Access Panels
Sometimes, your air duct cleaning professional will need to cut access panels to get at parts of the system to cool it. You should make sure the access panels are properly sealed after the cleaning.
Heat Exchanger Cleaning
Both the air-stream side of the heat exchanger and the secondary heat exchanger must be cleaned.

Remove, Clean, and Reinstall
The blower motor should be removed and cleaned, along with its housing and assembly. The blades must not have oil or other dust, nor should the blower compartment as a whole.

Clean Evaporator
The evaporator coil, pan, and drain must be cleaned. You should be able to point a flashlight at the coil and have the light shine through. If not, the coil is not clean.

Replace Air Filter
The dirty air filters should be removed and their replacements should match the efficiency rating recommended by the heating or cooling system’s manufacturer.

Wash the Air Cleaner
The air cleaner should also be washed as part of the air duct cleaning.

Clean Supply Ductwork
Make sure that the ductwork that send the air supply to the rooms in your house is cleaned.

Clean Return Ductwork
Check after the cleaning that the return ductwork, which sends air back to the heating or cooling device is clean.

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Glossary Of Terms
San Mateo County Glossary of Terms for Air Duct Cleaning Customers

When you want to know if your air ducts are going to be cleaned properly, you need to be able to discuss your system with your HVAC expert. Below are some terms that may help you be more comfortable with the conversation.

advanced reciprocating compressor
Kind of compressor used for improved efficiency when compression refrigerant for cooling.

air handler
In the heating and cooling systems for your house, the part that sends the air through the ductwork.

British thermal unit
Measure of heat. One BTU is roughly equivalent to the amount of heat that a wooden kitchen match gives off.

Also known as: BTU

annual fuel utilization efficiency
A rating on a furnace that indicates how efficiently the furnace uses fuel to make heat. Reported as a percentage. An AFUE of 90% indicates that 90% of fuel is producing heat, while 10% is leaving as exhaust due to combustion.

Also known as: AFUE

CFM
A measurement that shows the number of cubic feet of air that flow by a single point in sixty seconds. Higher numbers indicate greater air flow.

Also known as: cubic feet per minute

capacity
Refers to a system’s ability to affect a specified amount of space. Heating capacity is usually described in BTUs, while cooling capacity is usually described in tons.

carbon monoxide
A gas created by combusting carbon-based fuels when there is not sufficient air. It is highly dangerous, while being odorless.

compressor
A part of a heating or cooling system that determines how much pressure is put on the refrigerant. It is typically part of the outside unit.

condenser coil
The condenser coil is the part of a heating or cooling system that returns refrigerant from a gas to a liquid. Changing the state from gas to liquid extracts the heat. It is typically part of the outside unit.

DB
Unit of measurement for noise.

Also known as: dB, decibels

damper
A damper is part of duct work. It can open or shut to allow or cut off airflow.

downflow
Refers to a kind of furnace that moves cool air from the top and sends warm air to the bottom. Often used when a furnace is placed on the second floor.

ductwork
Pipes that send air from a system’s air handler to the vents located throughout the house.

Also known as: ducts
EER
A calculation that determines how efficient a device’s energy use is. The formula is to divide the device’s BTU by its wattage.

Also known as: energy efficiency ratings

electronic air cleaner
A kind of filter, it can remove large particles and contaminants from the air. For smaller particles, it magnetizes viruses, bacteria, and other tiny particles, then attracts them to a collection surface.

Also known as: EAC

energy saver switch
Makes an air conditioner’s fan and compressor switch on and off in sync, so that less energy is used.

Energy Star
A government program to label devices that offer better energy use than others in their category. This allows consumers to save on energy costs.

evaporator coil
Part of the indoor system for the heating or cooling system, it changes the state of the refrigerant from liquid to gas or vice versa, thus removing heat and humidity from the air.

Also known as: indoor coil

fan coil
A fan coil may be used instead of the furnace and evaporator coil. The fan coil is also an indoor part of the system, and it changes the state of the refrigerant from liquid to gas or vice versa to remove heat and humidity.

HEPA
A type of filter used to prevent particles from re-entering the surrounding space.

Also known as: high efficiency particle air

HSPF
Measurement used to describe how efficient a heat pump is. A higher number indicates more efficiency.

Also known as: heating seasonal performance factor

HVAC
The acronym for heating, ventilation, and air conditioning.

heat exchanger
A part of a furnace that moves heat to the surrounding air.

heat pump
A heat pump moves heat and cold in and out of the house. When used in cooling mode, it performs like an air conditioner to remove heat from the house. In heating mode, it uses heat from the outside to warm the house.

horizontal flow
A kind of furnace that takes air in one side and send it out warmer on the other side. Installed on its side, it is often the type used for attics or crawl spaces.

Also known as: horizontal heater

phantom load
The electricity that a device uses when it is plugged in and not turned on.

plenum
The plenum is sheet-metal box that allow more ductwork to connect to either the furnace outlet or the air handler outlet.

split system
A split system may be a heat pump or air conditioner. The components are installed in two locations, usually inside and outside.

two-stage compressor
A compressor that can operate at two different levels. When properly sized, the device operates 80% of the time at its low level, and 20% of its time at its high level. By operating at the lower level most of the time, the device improves efficiency and reduces humidity level and operational noise.

upflow
A furnace type. It pulls cool air in at the bottom and exhausts warmed air out the top. Often used in a basement installation.

ventilator
A device that gets heating or cooling energy from the indoors air and moves that energy to incoming air.

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Frequently Asked Questions
San Mateo County Air Duct Cleaning FAQ

Q: Why Choose a Diamond Certified Air Duct Cleaning Service in San Mateo County?

A: Diamond Certified helps you choose an air duct cleaner with confidence by offering a list of top-rated local companies who have passed the country’s most in-depth rating process. Only air duct cleaners rated Highest in Quality earn the prestigious Diamond Certified award. Most companies can’t pass the ratings. American Ratings Corporationalso monitors every Diamond Certified company with ongoing research and ratings. And your purchase is backed by the Diamond Certified Performance Guarantee. So you’ll feel confident choosing a Diamond Certified air duct cleaner.

Q: Should I call air duct companies who advertise cheap air ductcleaning specials?

A: Companies that offer very low prices for the whole house should be avoided. The rate is simply a teaser, designed to get the unwary to sign up. The customer is often then hit with charges that drive the price up.

You should know that in 1996, the EPA estimated air duct cleaning charges at between $450 and $1000.

Q: Does it matter whether the company uses a truck-mounted or portable vacuum?

A: When the air duct cleaning is done according to NADCA standards, either a portable or a truck-mounted vacuum can perform adequately. While a truck-mounted vacuum is usually more powerful, a portable vacuum may be able to be brought closer to the job itself. For all portable and handheld vacuums that exhaust into the house, it’s important to be sure they use HEPA filters.

Q: Why does it matter what my ducts are made of?

A: Fiberglass is present in much of modern ductwork, whether in the shape of fiberglass duct board, fiberglass lining for ducts, or flexduct. Older ductwork may be bare sheet metal. The distinction is important for several reasons. First, cleaning is performed by using a brush or other tool to loosen particles, which are then vacuumed up. The bristles on the brush must be soft when used with fiberglass, so that the fiberglass is not damaged. The air duct cleaning company must also be careful about using other tools instead of brushes – blowguns, air whips, and the like may not be appropriate for use with fiberglass. Secondly, once fiberglass is damaged by mold or water, it is recommended to replace it, rather than trying to fix or remediate it.

Q: Why is there mold on my ductwork?

A: Mold typically comes from damp that is allowed to linger. Damp can be a problem with a heating/cooling system if the coil is not properly drained. The coil is at the heart of the system and it is where refrigerant is changed from liquid to gas or vice versa. Changing the state of the refrigerant can remove humidity and heat or can bring heat in. The liquid/gas conversation can have condensation as a by-product. This condensation must drain properly so that mold does not take hold. This is one major source of mold.

Q: My air duct cleaning company showed me mold from my duct. I never noticed it. Are they right?

A: Some air duct cleaning companies will claim that you have mold in your ducts. You should ask for proof. The company may put a petri dish or similar collection device into the duct and then give you the resulting substance as proof that mold is present. Actually, no one can tell if mold is present visually. You should take the substance to a lab and get it tested to be sure it is actually mold.

Q: My air duct cleaning company wants to put a sealant in my ducts. Should I let them?
A: First, ask what the sealant is designed to do. Some sealants are offered with the claim that they will reduce the movement of dust and particles in the ductwork. You should not accept these sealants. First, the sealant will probably be applied by being sprayed into the duct. You cannot guarantee that the sealant will cover the entire surface properly. Secondly, for ducts with fiberglass, the sealant may harm their ability to resist fire and provide better acoustics. The sealant might even void the fiberglass manufacturer’s warranty.

Other types of sealants, such as sealants to mend fiberglass or for fire resistance, might be appropriate for use. Ask what the purpose of the sealant is, how it will affect your warranties, and how you will know that it is working.

Q: My air duct cleaner wants to spray some anti-microbial chemicals in my ductwork. Is that ok?
A: You should approach the use of chemicals in your air ducts very carefully. Sometimes air duct cleaning companies recommend chemicals to fight bacteria or mold. First, you have to consider how you or family members might react to the chemical. Second, you should ask to see the chemical’s label. You should make sure the chemical is being used for one of the purposes identified on the label – otherwise it should not be used. You should also check how the label says the chemical should be applied. If the chemical cannot be applied as directed on the label, it should not be used. For example, if a water rinse is required, it cannot be used in ductwork because water should not be introduced. With caution, chemicals approved for it may be used on bare sheet metal surfaces.

There are no chemicals approved for use on fiberglass or flexduct, or any fiberglass material. If these materials have mold, they should be replaced.

Rather than using chemicals at all, you should search for the source of the problem and try to eliminate it. For example, mold can be eliminated if it is caused by poor condensation drainage if you fix the way the condensation is draining.

Q: What can I do to prolong the life of my air duct cleaning service?

A: Air duct cleaners in San Mateo County estimate that a clean lasts three to seven years, depending on who lives in the house, heating/cooling usage, the local climate, and the like. Your best way to preserve a clean heating/cooling system is to prevent dirt and water from entering. Make sure the draining in the system is handled correctly. Change air filters annually (at the same time, it’s good to do carbon monoxide testing). Make sure that you are not missing filters, and that the filter holders do not allow air to pass around the filter. Vacuum the house regularly to prevent dirt build up. If you have a major renovation project in the house, seal off the registers and don’t run the system until you have cleaned up after the project. Make sure ducts are sealed and insulated unless they are in air conditioned spaces.

Q: I can see dust on the vents where air flows in my house. Do I need air duct cleaning?

A: You may see dust on the registers, or grilles, where air flows into and out of your heating/cooling system. This does not automatically mean that you should get your air ducts cleaned. You can easily vacuum the grilles clean, or other wise clean them. It is normal for the grilles to accumulate dust over time. Look for large buildups of dust in the vents themselves to determine if you need an air duct cleaning because of dust.

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