Interesting. Giuliano Cuete and Carlo Olcese have the exact same post about pretenders and being NADCA certified, word for word. So how do you become NADCA certified? And does that mean you are not a scam artist or a "blow and do" ripoff? hmmm, interesting. The EPA says that under normal conditions, a properly maintained system should NEVER need it's ducts cleaned.
I turned on the AC when he was finished and immediately saw black fuzz balls the size of marbles come out of several of the registers. He said that was expected since everything was shaken up. So much for describing the service as cleaning. I paid him and sent him on his way. I cannot imagine that this type of service is worthwhile in anything but a new house. Apparently in old houses such as mine I can expect that using a whole house humidifier in the winter followed by a great AC can loosen the soot. Maybe this is to be expected for the first few weeks of summer each year. I now have lined the inside of the registers with cheesecloth to catch the fuzz. I’ll see if it stops after a couple of weeks.
Refrigerant Metering Device -- Every HVAC system has one of these, and heat pumps have two. They regulate the amount of refrigerant going through your air-conditioner. If it fails, either too much or too little refrigerant will course along the lines and either not perform well or will overwhelm the compressor and cause it to fail. A total failure of this component will result in a complete loss of operation.
I am NADCA Certified Air Systems Cleaning Specialist. Over the years I have learned on simple answer to this questions: there air duct cleaners and there are pretenders. There will be no benefit at all if you use on the very cheap pretender because they will not really clean anything. On the other hand if you call a qualified air duct cleaner with a NADCA Certification you will, like 99% of my customers, report improvement with your respiratory problems, you will see less dust and the job will pay for itself with energy savings and repair prevention.
fact is most homes have bad filter racks. when you insert the filter it doesn’t seal well to the sides so some of the air and dust bypass it and end up in the supply ductwork and into the house. Most of the dust in the supply ductwork settles down and doesn’t get blown in the house but some of it does when the blower starts up or when you put a new filter. If you have allergies or other health problems put in an electronic air cleaner, get your ducts cleaned and run the fan as much as you can afford. you can also get an ECM motor installed which is going to be worth it if you want to run the fan 24/7. If you have uninsulated metal ducts take down the ones you can and wash them. Then put them back and seal the joints. Cleaning the ductwork also improves airflow which is important to AC and Heat pump systems for efficiency. An electronic air cleaner will also improve airflow and static pressure because they usually have a much larger filter surface area. An electronic air cleaner also keeps the ac coil clean like new which means better efficiency and no cleaning needed. AC furnaces sometimes grow mold around the coil because of the condensation. Electronic air cleaners should be able to filter mold spores but the best remedy is installing a UV light next to the coil which will kill the mold.
Good article, but it fails to point out that leaky return-side ducts could be drawing dust and allergens into the duct system from the enclosed spaces in which they run, e.g. between walls, below floors, attic. So duct cleaning may only be a temporary solution. The homeowner can get a home energy audit -- free in many states -- to determine if they have significant duct leakage. An Aeroseal dealer may be able to effectively seal up the duct system without needing to tear into walls etc to get to the ducts.
I guess I should present my credentials first, I am a 30 year veteran of the heating and cooling industry. I started at the bottom and have participated in every area of the trade. Installer, service, maint. Ownership, rep, territory manager and so on. A forced air duct system is a large vacume. Like your vacume it has an air intake (return air) and an exhaust (supply registers). A filter just like a vacume (located next to furnace or air handler). Now I want you to visualize something. Put your head inside your vacume cleaner and breath. Get the picture? This is what your duct work looks like. Do you clean your vacume when it’s dirty? If it’s full and the filter is dirty you lose performance and it starts poluting the air you breathe. It’s common sense. I recommend hiring a duct cleaning outfit that you have researched to be honest, background checked, drug tested, insured, and highly recommended by your piers in the area. The service is a necessity, but like everything, it should be done by a qualified company.
An important component of natural ventilation is air change rate or air changes per hour: the hourly rate of ventilation divided by the volume of the space. For example, six air changes per hour means an amount of new air, equal to the volume of the space, is added every ten minutes. For human comfort, a minimum of four air changes per hour is typical, though warehouses might have only two. Too high of an air change rate may be uncomfortable, akin to a wind tunnel which have thousands of changes per hour. The highest air change rates are for crowded spaces, bars, night clubs, commercial kitchens at around 30 to 50 air changes per hour.[17]

Very interesting article. I searched articles about services for cleaning ventilation systems. But I have some questions. For cleaning ventilation system used special products for cleaning. Can I know in company manager about, which type of cleaning products they use? Your family members may be allergic in some components. It’s very big problem. And one more problem it’s how to choose the right company in Internet. Sometimes I don’t have much time to find a company in my town and I use the Internet. But I find a lot of company. It is very popular services, for example, Stanley Steemer – or my local not very popular service, for example, AllstatesAirDuctPro – Can I understand the company is professional or not, only looking through the website? What must I check on the website? Who has helpful information? I will very grateful for your help. Links I add for understanding my problem. They are random and not for advertising.
Your contractor will do a load calculation to determine the proper central air conditioning unit for your home. This calculation accounts for the climate, size, shape and orientation of your home, as well as its square footage. A professional will also look at the insulation, windows, walls, floors and other materials that compose your home. He/she will then examine any leaks, seals and existing ducts or vents.

Consider what kind of heating and cooling system you want installed for the square footage of your home. Do you want a full system with a thermostat or a specific machine for the summer like a swamp cooler? Do you need a new furnace just for the winter? For any of these projects, the cost will vary depending on the quality, style and machine size you choose. If you have a tight budget, think of going smaller and upgrading over time. For example, if you can't afford to convert your entire home to solar power, you may want to consider only utilizing it to heat your water. Some other types of heating systems are:
Had duct cleaned (apartment) however, dust is still settling throughout the apartment. Contractor said no other cleaning necessary until two (2) years. Is there a time period before dust no longer settles prior to that time? Should the vendor had worn a mask? He did not cover his face the vents and dust was blown throughout the apartment (had family help with the cleanup). I had to leave when they left because I have asthma and I couldn’t breathe without coughing. Please help!

You may consider having your air ducts cleaned simply because it seems logical that air ducts will get dirty over time and should be occasionally cleaned. Provided that the cleaning is done properly, no evidence suggests that such cleaning would be detrimental. EPA does not recommend that the air ducts be cleaned routinely, but only as needed. EPA does, however, recommend that if you have a fuel burning furnace, stove or fireplace, they be inspected for proper functioning and serviced before each heating season to protect against carbon monoxide poisoning.