Air duct cleaning is not vacuuming a few vents. A proper cleaning is a push and a pull. Compressed air pushes the dust off the walls of your ductwork, and a powerful vacuum pulls it out of your home. This guide shows how our crew does it, with a HyperVac 220V portable vacuum and an air compressor rated at 175 PSI or more.
The Short Version
Push pull duct cleaning has two halves that work together. The push is compressed air from an air whip that thrashes inside the duct and breaks dust and debris loose. The pull is negative air from a portable HEPA vacuum that is hosed to the furnace and keeps the whole system under suction, so the loosened dust travels to the vacuum instead of into your rooms.
- The vacuum connects at the furnace and keeps the entire duct system under negative pressure
- An air whip fed by a compressor of at least 175 PSI agitates each branch and the main trunk line
- Dust travels with the airflow to the vacuum, where HEPA filters hold the fine particles
- Every access hole is sealed and every vent is photographed before and after
See A Cleaning Step By Step
The picture shows a typical basement furnace setup. The vacuum sits by the furnace, the technician works from the main floor and the basement, and the compressor feeds the air whip.
The crew tours the home with you, finds the furnace and the main trunk line and turns the furnace off. Registers that are not being worked get covers so the suction goes where it is needed.
Good to know Every home is different, so we look at the layout before we set up anything.
Tap the numbers to jump around, press Play the tour for a guided run, or tap a tool name to find it in the picture. The speed, airflow and animation controls are under the picture.
What Push Pull Means
Push pull is source removal done with air. It matches what NADCA, the National Air Duct Cleaners Association, describes as the two parts of a proper cleaning, which are breaking contaminants loose and then collecting them while the system stays under continuous negative pressure. You can read NADCA's description of proper cleaning methods for yourself.
The Push
The push is agitation. A flexible airline carries compressed air to a whip head that thrashes inside the duct. NADCA lists air whips, brushes and compressed air nozzles or skipper balls as agitation tools. The whip reaches around bends and down long runs, and the moving air lifts packed dust off the metal and into the airstream.
The Pull
The pull is negative air. The HyperVac 220V is connected to the system at the furnace and pulls air through every open register, down the branches and along the trunk into the machine. Because the pressure inside the ducts is lower than the pressure in your rooms, air and dust flow toward the vacuum and not out into the house.
Why You Need Both
Agitation without suction only moves dust around. Suction without agitation picks up the loose layer on top and leaves the packed buildup stuck to the walls. The EPA warns in its guidance on duct cleaning that an inadequate vacuum collection system can release more dust than leaving the ducts alone, which is why the pull is not optional.
The Equipment
These are the tools that make push pull work. If a company cannot tell you what it uses for each job, ask more questions before you book.
| Tool | Its job | What we use |
|---|---|---|
| Portable vacuum | The pull. Keeps the whole system under negative air and filters what it collects. | HyperVac 220V, 5000 CFM, HEPA filtration |
| Air compressor | The push. Powers the air whips. | Gas powered, two stage, 23 CFM, 175 PSI |
| Air whips | Loosen dust from duct walls, bends and long runs. | Air whips on flexible airlines, plus agitation tools |
| 8 inch hose and furnace collar | Carry the dust from the system to the vacuum. | A large corrugated hose from the top of the HyperVac to the furnace plenum |
| Plugs and sheet metal plates | Close the holes the tools used. | On every access hole |
| Camera | Documents the work. | Before and after photos of every vent |
Why 175 PSI Is The Minimum
Compressed air does the pushing, so the compressor sets how hard the whip can hit. Our minimum is 175 PSI from a gas powered compressor, and we suggest asking any company about it. A weaker compressor can leave packed dust stuck to the metal even when the vacuum is strong.
Why The HyperVac 220V
The HyperVac is a portable negative air machine, so it comes into the home instead of staying on a truck outside. It plugs into 220 volt power and is rated at 5000 CFM. NADCA says both portable and truck mounted vacuums can be used. What matters is steady suction at the duct, HEPA filtration and a tight connection.
Step By Step In A Basement
Here is what happens on a typical job, in the same order as the animation.
1. Walk the job and shut down the furnace
We arrive on time, meet you and tour the home to see the layout of the ductwork. We find the furnace and the main trunk lines, turn the furnace off and cover the registers that will not be worked so the suction goes where we need it. We answer your questions before any tool comes out.
2. Plug the HyperVac 220V into the furnace
The HyperVac is set up near the furnace and plugged into 220 volt power. A large 8 inch hose runs from the top of the vacuum to a collar on the furnace plenum, the box where the supply trunk line begins. That hose is how the dust is collected, and it makes the whole duct system one sealed path to the vacuum. If a connection leaks, suction drops, so we check it before we start.
3. Turn on negative air
With the vacuum running, air is pulled through every open register, down the branches, along the trunk line and into the machine. The system stays under continuous negative pressure for the whole job, which keeps dust from spreading and captures the fine particles that become airborne while the ducts are disturbed.
4. Push through the branches
We work through the floor vents one at a time, and then walk over and clean the return vent the same way. At each vent the technician feeds the air whip down the branch. The compressed air thrashes the whip against the inside of the duct, and the dust it knocks loose rides the airflow toward the trunk and the vacuum. We take before and after photos at each vent to be sure our tools went the right direction and the line is clean.
5. Open the trunk line
The main trunk lines get two access holes about 8 inches wide, one in the supply trunk and one in the return trunk, so the tools can get inside both. Where an existing opening can be used, we use it. NADCA notes that making these openings and closing them again takes craftsmanship.
6. Push in the trunk
In the basement the technician feeds the air whip into the supply trunk line and works it along the run, then moves to the return trunk and cleans that too. The trunks are the main roads that every branch feeds into, so they usually hold the most buildup. The whip thrashes against the walls and lifts the dust layer into the airflow.
7. Pull it all to the vacuum
The loosened dust rides the airflow along the trunk, into the plenum, through the hose and into the HyperVac. HEPA filters hold the fine particles so they are not blown back into your home. Once the trunk lines are clean, we clean the furnace itself.
8. Seal it up and show you the photos
We patch every hole with plugs and sheet metal plates, take down the equipment and load it into the truck, and clean up after ourselves. The furnace goes back on, and we walk you through the before and after photos of every vent and answer your questions.
Why The Trunk Line Is The Main Event
Think of the trunk as the highway of your duct system. Air leaves the furnace and travels down it before it branches off to each room, and on the return side everything flows back to the furnace through a trunk of its own. Dust knocked out of a branch ends up in the trunk, so a cleaning that skips the trunk can leave the system recontaminating itself. NADCA says that failing to clean all components of the system can recontaminate the whole thing.
Connecting the vacuum at the furnace end gives every branch a clear path to it, and the technician can work the trunk from the basement while the suction keeps pulling.
More Than Just The Ducts
NADCA lists the parts of an HVAC system that should be cleaned, including the ducts, registers and grilles, plenum, blower assembly, heat exchanger, coils, drain pan and filters. SimpliHome cleans the supply and return vents, the branches, the main trunk lines and the furnace on every job. Dust left in the furnace or blower can find its way back into freshly cleaned ducts.
Push Pull Compared With Other Methods
| Method | How it works | Limits |
|---|---|---|
| Shop vac | A household style vacuum on the vent opening. | Reaches only a few feet into each opening and leaves most of the ductwork untouched. |
| Vacuum and rotary brush | A longer hose and a spinning brush that loosens debris as it goes. | Better than a shop vac, but the vacuum may not pull hard enough to lift clogged debris, and a spinning brush can harm delicate duct interiors. |
| Push pull | Compressed air whips loosen the debris while a HEPA negative air vacuum pulls it out of the whole system. | Needs real equipment, including a compressor of at least 175 PSI and a vacuum with strong suction, plus careful work around fragile duct. |
When Cleaning Is Not The Answer
Push pull is the right way to clean a metal duct system, but it does not fix every problem. The EPA, NADCA and others point out several cases where something else is needed.
- Mold inside fiberglass duct liner or duct board. The EPA, NADCA and NAIMA recommend replacing wet or moldy fiberglass duct material, because cleaning is not enough to stop it from growing back
- Torn or crushed flexible duct. It can be brushed, but replacing accessible flex duct can cost less than cleaning it
- A moisture problem. The EPA says to fix the cause of the moisture first, or the problem is likely to return
- Steam and other wet methods, which the EPA says should not be used on any kind of ductwork
- Chemical biocides and sealants. The EPA says research has not shown they work in ducts, and no biocides are registered for use in internally insulated duct systems
The EPA also says duct cleaning is not recommended routinely but only as needed, such as when there is substantial mold in hard surface ducts, a vermin infestation or ducts clogged with excessive dust and debris. For an honest look at the tradeoffs, read the downsides of duct cleaning.
How Long It Takes And What You Will See
Most homes take three to five hours, and a larger home with two furnaces can take most of the day. Our post on what happens during a visit walks through the time. When we finish, you see before and after photos of every vent.
To see what a cleaning costs, try the calculator in our Brookfield pricing guide. SimpliHome is a family owned company based in Brookfield, and our air duct cleaning service covers Waukesha County and Milwaukee County. When you are ready, get a free quote or call (262) 289-1035.
How Duct Cleaning Works Questions
What does push pull mean in duct cleaning?
Push is the compressed air from an air whip that loosens dust from the duct walls. Pull is the negative air from a powerful vacuum that carries the dust out of the system. Doing both together is how a duct system actually gets clean.
Why does the air compressor need to be 175 PSI?
The compressor sets how hard the air whip can hit. Our minimum is 175 PSI, because a weaker compressor can fail to loosen packed dust from the metal.
What is a HyperVac 220V?
It is a portable negative air duct cleaning vacuum that plugs into 220 volt power. SimpliHome uses one rated at 5000 CFM with HEPA filtration, and connects it to your system with a hose at the furnace.
Why do you connect the vacuum to the furnace?
The furnace plenum is where the supply trunk line begins, so a connection there gives every branch a clear path to the vacuum. The furnace is turned off first, and it is cleaned too before we finish.
Does the vacuum blow dust back into my house?
No. During a proper cleaning the system is under negative pressure, so air flows toward the vacuum. HEPA filters hold the fine particles. The EPA says to use vacuum equipment that exhausts outside the home, or HEPA equipment if it exhausts inside.
Do you have to cut holes in my ducts?
Often in the main trunk lines, about 8 inches wide. Existing openings are used when they can be. Every hole is closed with plugs and sheet metal plates, and the EPA says access holes must be sealed airtight.
Is a duct cleaning messy?
It should not be. Negative air keeps the dust moving toward the vacuum, and covering registers and protecting floors keeps the work tidy. We clean up after ourselves.
Do I need to be home?
It helps. Someone should let the crew in and be there at the end to see the before and after photos.