September 17, 2026

Plan the extraction system before the first machine is installed

Our old exhaust system wasn't broken. Still, it was left behind when we moved to the new woodshop. What kept us busy while planning the new one wasn't just the question of which system to choose, but above all the timing and location. After all, if you wait to plan until the machines are in place, you no longer have a choice about where to put it.

A clean air unit removed from the old exhaust system, stored in a storage room — It still worked. But it wasn't a good fit for the new workshop anyway.

The old system was running—and no longer fit the bill

She did her job for years. Nevertheless, four factors led us to decide not to take her with us:

It didn’t have enough capacity for the machinery that had grown up around it: it was designed for about four machines, but in the end there were eight connected to it, and it was never intended for simultaneous operation. Some of the dampers had to be operated by hand, which meant that if you forgot to do so, you’d be sucking air from the wrong place. The heat escaped outside along with the air. And in woodworking shops, about 29 percent of heat loss occurs through the chip and paint mist extraction system. Plus, the chip bags had to be changed frequently, and the filters had to be cleaned.

None of these issues is a flaw in the system. It was properly designed at one time but failed to keep pace with growth. To put this in perspective: When it comes to electricity consumption, the exhaust system in a woodworking shop uses the most power—not the saws, not the routers.

Not beside it, but above it

There were two obvious options for the new structure: placing it outside or inside the workshop. We chose a third option and installed it on the storage platform directly above the woodshop.

There are several reasons for this:

The purified air remains inside the building, and because the hall and the woodshop are connected by doors that are kept open at all times, the heat stays where the work is being done.
From the pipe network beneath the ceiling, the air travels a short distance straight up into the system. Every meter and every bend results in a loss of pressure, and wherever the air slows down, material accumulates.
The facility does not occupy any production space.
The noise from the fan comes from a level above the workstations, not next to them, and the system itself is soundproofed.

Perspective drawing from the design phase: The dust collector is located on the storage platform, and the pipe network runs beneath it with branches leading to the machines — The concept in a picture: System at the top, distribution at the bottom (Graphic: Miller GmbH)

Whether this is even possible depends on the design. Our system is a Spänex dust collector: It is designed and tested so that the cleaned air can be recirculated into the workspace. A system intended for outdoor use must meet different requirements—including those related to airflow—and cannot simply be placed inside the facility. If you’re planning to install a system, you need to know in advance where it will be located.

Dust collector on the storage platform above the woodworking shop, with the exhaust pipe rising from the floor next to it — Shortly after installation: the plans became reality

How many machines are running at the same time?

The system was designed and delivered by Miller GmbH in Leutkirch. For the design calculations, each machine was specified, including the number of connections and their diameters. We also worked together to determine which machines often run simultaneously and which ones rarely do. This was precisely what the old system did not account for. Today, work can be carried out on multiple machines at the same time.

The principle behind this is a simple rule: The sum of the cross-sectional areas of all open connections at any given time must not exceed the cross-sectional area of the main line. If it does, the air velocity in the line decreases. And at speeds below about 20 m/s, the air can no longer reliably carry the chips, causing material to accumulate in the pipe.

The key factor, therefore, is not the number of machines, but how many of them are in operation at the same time. Anyone who connects a machine without checking this will reduce the speed for all the others as well. The extraction capacity is also greatly influenced by the pipe diameter and the number of bends.

Excerpt from the workshop floor plan showing the piping network and the connections to the individual machines — Each machine with its connection shown on the floor plan—this forms the basis for the layout (Graphic: Miller GmbH)

The system controls using

The reverse scenario is just as important. If only one small machine is running, there isn’t enough air flowing through the main line. The control system then opens additional valves on machines that are currently idle to ensure that enough air is circulating again. This supplemental air does not supply the machine, but rather the line. As soon as additional machines start up, the control system closes the valves in reverse order to reduce the supplemental airflow.

Added to that is the speed control. The fan runs only as fast as current demand requires, rather than always at full power. And the filters are automatically cleaned with bursts of compressed air as soon as the fan shuts off and a set runtime is reached. That’s the difference from the old system: It always ran at the same speed, and cleaning was done only when someone got around to it.

First the machines, then the pipes, then the ceiling

Before placing the order, therefore, a plan was drawn up: where each machine would be located, where the pipe would run, and where openings would need to be cut in the ceiling. The location and size of the openings were communicated to everyone involved before construction began. The installation had been cleared in advance with the structural engineer—with an empty weight of about 850 kg on a platform, this is no mere formality. And because the system has an automatic fire suppression system, a water line to the platform was also included in the planning.

Detail from the design: the two pipes on the dust collector and their openings in the floor of the storage platform, with dimensions — This is how the tunnel was planned—the location and diameter were determined before construction began (Graphic: Miller GmbH)

What Should Not Go Into the Filter

We learned a lesson from the old system. We also regularly cut cardboard for our packaging, and cardboard clogs the filters in the exhaust system. We had previously cleared this with our equipment manufacturer—that we would be extracting it through the system. But it doesn’t have to be cardboard at all: edge strips from the edge bander, offcuts from the sliding table saw, plastic shavings. Anything that’s light, flat, and long travels through the duct and gets stuck somewhere.

That is why the new system includes a material separator located directly behind the sliding table saw, well before the filter. Without it, everything travels the long way to the system, and anything that gets left behind along the way isn't detected until the suction weakens.

A material separator in the exhaust line directly behind the sliding table saw, with a box of offcuts next to it — Catches what doesn't belong in the filter: the material separator behind the sliding table saw

Room for improvement

Eight machines are connected to the system, and nine pipes have been laid. The ninth pipe is already in place for the next machine, and the control system is designed to handle up to sixteen machines. Nevertheless, each additional machine must be integrated into the control system later, and the system must then be recalibrated.

To change the bags, the chip containers must be pulled out. The area in front of them must remain clear at all times on the platform, but on the other hand, the system is not located outdoors, where it would be exposed to heat, cold, and the elements.

What we haven't decided yet

At our facility, the wood chips are collected in containers lined with chip bags. A briquetting press would be an option; it would reduce the volume of the chips and turn them into fuel right away.

There are two reasons why this wouldn't work for us. With the volume we produce, we don't generate enough wood chips to make the press cost-effective. And we regularly cut other materials, such as cardboard and, in some cases, plastics. No one can use what's left over from that as fuel.

Three chip bins with chip bags inserted, located beneath the dust collector — Three containers with a chip bag underneath the machine. It remains to be seen whether they will ever be turned into briquettes.

How do you handle this at your facility—chip bags, a silo, or a baler?

Our stage was planned for the new building. In the existing building, it’s usually the adjoining room or the outdoor space that’s used, which have different requirements. The order remains the same: first the machine locations, then the pipes, and finally the space for the system.

Read more: Hand-held machines fall into their own category, with different requirements. We've written a separate article on portable extraction systems.

Sources: TRGS 553 “Wood Dust” · DIN EN 16770 “Extraction Systems for Wood Dust and Chips for Indoor Installation” and DIN EN 12779 “Stationary Extraction Systems for Wood Dust and Chips” · Test Principle GS-HO-07, Residual Dust Content Class H3 · Energy Performance Indicators: SME Initiative for the Energy Transition and Climate Protection, Carpentry Trade · Electricity Consumption of the Exhaust System: Furniture Manufacturing 07/2018 · Planning and Graphics: Miller GmbH, Leutkirch