Ventless coffee roaster: can your space handle one? (2026)

Q: Do I need a sample roaster as well?

It depends on what the sample is for. Which https://sciencebrewing.com/sample-roaster/ a roastery needs, and when none is needed, is covered separately.

The key points in 30 seconds

Smoke is the hard problem. That is why most coffee roasters have a chimney.
Every way of cleaning the smoke inside the machine has a price: power, maintenance or both. Ask which.
A 10 A circuit at 230 V gives 2.3 kW. Machines with afterburners usually need more.
All the power the machine draws turns into heat in the room.
Whether you need an environmental permit depends on your country and your volume. Ask your local authority.
What you cannot work out yourself, you ask three people: your electrician, your landlord and your local authority. The questions are below.

It is not the machine that stops your roastery. It is the room.

This is how it usually goes. You find a coffee roaster you like. You run the numbers on the coffee. Everything looks good.

Then someone asks where the smoke is going to go.

That is when the second project starts. A duct up through the roof. Fire-rated penetrations. Chimney sweeping. A landlord who has to approve a hole in the building. Neighbours who have to put up with the smell every day. And when it is all done, the roastery is stuck in one room. We have spoken to roasteries in Sweden that had to move when the neighbours ran out of patience. Moving with a duct is not a move. It is a new installation.

That is why more and more people are looking for a coffee roaster without a chimney. This guide gives you everything you need to decide whether your space can handle one. You can do the whole test yourself. It takes about fifteen minutes.

What is a ventless coffee roaster?

A ventless coffee roaster is a machine that cleans its own exhaust so it can be released into the room instead of through a duct. It needs no chimney and no hole in the building.

That does not mean the room has no requirements. The smoke is dealt with. The heat, the moisture and the smell remain, and the cleaning system needs maintenance.

Why do almost all coffee roasteries have a chimney?

Because smoke is difficult. A roast releases fine particles, oils, water vapour and a mix of strong-smelling gases. The easiest way to get rid of all that is to send it out of the building. That is why most coffee roasters, gas and electric alike, have a duct running up over the roof. With the duct come chimney sweeping, fire-rated penetrations and often an afterburner on the way out.

The trend in recent years is to deal with the smoke inside the machine instead. It works. But no solution is free. Every technology costs power, space, maintenance or all three.

Which technologies clean the smoke inside the machine?

There is more than the afterburner. Here are the common ones, and what each of them costs you.

Technology	How it works	What it removes	What it costs you
Thermal afterburner	Heats the exhaust until the smoke burns off	Particles, odour, gases	A lot of power, both running and heating up. A lot of heat in the room
Catalytic afterburner	A catalyst breaks the smoke down at a lower temperature	Odour, gases, some particles	Still several kW. The catalyst clogs and has to be cleaned, regenerated or replaced
Electrostatic filter	Charges the particles and catches them on plates	Particles and visible smoke	Little power. Does not remove odour. The plates need cleaning
Water scrubber	Passes the exhaust through water that cools and captures	Particles, oils, some odour. Cools the exhaust	Little power. The water gets dirty and has to be changed
HEPA and activated carbon	Mechanical filter plus carbon that binds odours	Fine particles, odour	Little power. Filters and carbon saturate and have to be replaced

None of them does everything. That is why they are often combined in several stages.

Four routes, sorted by what your space needs

	1. Chimney	2. No built-in cleaning	3. Afterburner in the machine	4. Filtration and scrubbing in the machine
Most common for	Most coffee roasters	Small roasters around 1 kg	Ventless roasters for cafés	Ventless roasters for a normal socket
Chimney or duct	Yes, with sweeping	Yes, a hose or duct you arrange yourself	No	No
Typical power	Three-phase or gas	Normal socket	Dedicated circuit, several kW	Normal socket on its own circuit
Ongoing maintenance for the smoke	Sweeping, duct cleaning	Duct cleaning	Cleaning or replacing the catalyst	Water changes, filters and carbon
Suits	Large volumes, own premises	Starting small	A café that can add a new circuit	A space with no duct and no new circuit

Why power makes such a difference. Burning smoke takes a high temperature, and a high temperature costs power. An electric afterburner alone can draw more than 3 kW, more than a whole 10 A circuit. Filtration and scrubbing need almost no power. The price is paid in maintenance instead: water, filters and carbon.

A machine running on 230 V tells you nothing on its own. Small roasters without built-in cleaning do too. What you are looking for is the combination: a normal socket and built-in smoke handling and enough capacity for your business.

The Space Test: eight questions that decide whether your room can handle it

Work through them in order. The first three stop the most people. Take the test here and you get the answer point by point, plus a report with the questions for your electrician, landlord and local authority. The same points are written out below the test.

What fuse is on the socket?This is where most people fall

The rule: amps × 230 = watts. It applies to the whole circuit, not the socket. It assumes 230 V, as in Europe and the UK.

Circuit rating	Limit for everything on the circuit
10 A	about 2,300 W
16 A	about 3,700 W
Three-phase 16 A	about 11,000 W

Work it out yourself:

Item	Watts
Roaster power (from the manufacturer)
+ everything else on the same circuit that can run at the same time
Circuit rating
= total	–
Is the total under the limit?	–

Enter the roaster’s power and we will do the maths.

Three-phase: a single-phase machine still only gets about 3,680 W on its phase, so choose 16 A.

Row of circuit breakers marked C10 and C16 in an open fuse board — Circuit breakers in a fuse board. The marking shows the rating, here 10 and 16 amps.

The trap: the socket in your back room shares a circuit with the dishwasher, the kettle or the fridge. Find the circuit list in the fuse board. If it is not there, ask your electrician.

Calculate with the machine’s peak power, not its average. Most roasters draw the most while heating up. A machine close to the circuit’s limit should have the circuit to itself.

If the circuit is shared with the kettle or the microwave, a routine can also solve it: do not use them while the machine roasts, and put up a note. Or run the roaster from another circuit.

Ask your electrician: What is the circuit rated at, what else is on it, and can the roaster have a circuit where nothing else large runs?

Where does the smoke go?

“Ventless” is not a protected term. It can mean burning, filtering, or a hose you have to run yourself.

Ask the supplier: Which technology cleans the smoke? Is the machine made for indoor use without extraction, and does the manual say so? What does the cleaning cost in power and maintenance, and how often? What happens if a filter is full or the water runs out?

Where does the heat go?

The rule: without a duct, practically every kilowatt the machine draws becomes a kilowatt of heat in the room.

A coffee roaster drawing 2 kW for hours heats roughly like one electric radiator on full. In a storeroom with no window you will notice it by lunchtime.

Ask the supplier: What room temperature is the machine designed for?

Ask your landlord: Can the room’s ventilation handle a couple of extra kilowatts?

Where does the moisture go?

The rule: around 16 percent of the weight disappears during roasting, and most of it is water and gas.

Work it out yourself:

Item	Value
Kilos of green coffee you roast per hour
× 0.16	–
= roughly how much water and gas leaves the beans each hour	–

If you roast four kilos an hour, that is more than half a kilo an hour. It ends up in the air, in a condenser or in the cleaning system. If the cleaning uses water, two more things come with it: topping up and changing. The water gets dirty as it captures the smoke and has to be poured away. Darker roasts dirty it faster.

Ask the supplier: Where does the moisture go? How often does the water need changing at your roast level and volume, and where may it be poured away?

Ask your local authority or water company: May the dirty water go down a normal drain?

Where could a fire start, and who is there when it does?

The chaff that comes off during roasting is dry and light. It burns when it meets an open flame or a high enough temperature. In a roaster both risks sit in the same place: in the drum and in the hot exhaust that carries the chaff on to the collector. That goes for gas and electric.

Machines differ in how they handle it. If the exhaust is cooled, for example with water, the temperature after cooling drops and so does the fire risk. Ask where in the chain the chaff collects, before or after cooling, and what happens if something goes wrong.

If the machine is to run when nobody is in the room, that is two questions, not one. The manufacturer answers whether the machine is built for it. Your insurer answers whether you are allowed.

Ask the supplier: Is the machine built for unattended running, and which safety features stop it if something goes wrong? Where does the chaff collect, and how often must it be emptied?

Ask your insurer: May the machine run unattended, and on what conditions?

Who smells it and hears the fan?

Cleaning removes the smoke. The smell of roasted coffee remains, most of all while the beans cool. In most countries the local authority can act on odour that bothers neighbours, even when the business needs no permit.

In front of your guests it makes the biggest impression. The machine is built to stand there: enclosed, with a guard on the cooling tray and ON/OFF as the only control. The smell and the fan noise still come with it, so run a roast in the room before you settle on the spot.

Ask the supplier: Noise level in dB, and how was it measured?

Do your lease and the planning rules say yes?

The lease states what the premises may be used for. “Café” does not automatically mean “producing coffee for sale”.

A change of use can require planning permission or building approval. A café roasting in a back room is a different question from an office turning into a roastery. Check the floor too: machines in this class weigh from around 15 kg to nearly 200 kg.

Ask your landlord: Does roasting fit the permitted use in the lease?

Ask the planning or building authority: Does the change need permission?

What do the authorities say?

Food. Roasting is food production. In the EU and the UK a food business has to be registered with the competent authority before it starts. If you are already registered as a café or restaurant, report the change.

Environment. Some countries have permit or notification thresholds for coffee roasting based on annual volume. In Sweden, for example, notification is required above 100 tonnes a year. Check the rules where you are, and whether your local authority charges fees for small-scale roasting.

We have written a food safety plan template for coffee roasteries: hazard analysis, routines, logs and a registration checklist. It is a Word file in Swedish, and the link comes with your Space Report when you take the test above.

Ask your local authority: Is our current registration enough? Are there permits, fees or volume limits for small-scale coffee roasting?

Did you pass all eight?

Yes to all: your room can handle a coffee roaster without a chimney. The next question is which one.
No to 1: you need a machine that runs from a normal socket, or an electrician.
No to 2 or 3: you need a duct or a different room.
No to 7 or 8: solve that before you buy anything at all.

Can you roast coffee outdoors or at a food truck?

Yes. A coffee roaster that does not need a chimney does not need a room either.

The plume is visible, and it draws people in. The cleaning deals with the smoke. But the exhaust contains a lot of water vapour, and most of it comes from the green coffee. You can see it from a distance. Together with the smell of freshly roasted coffee, it is a sign nobody else in the queue has.

Indoors the same vapour is a moisture question, see point 4. Outdoors it can go wherever it likes.

Three things to sort out first:

The socket. The roaster should have its own circuit. Ask the organiser whether you can have one, and whether the socket has residual current protection. With a generator: it must handle the machine’s peak power, which is often during heat-up, plus everything else in the truck. Also ask the manufacturer what the lowest temperature is that the machine can handle.
The organiser. Tell them in advance that what they see is steam, so nobody raises the alarm.
The authorities. Roasting is production. Ask whether it fits a mobile food registration or needs fixed premises. The simplest set-up: roast at your base, sell and show it off on site.

Which route is yours?

You have your own premises, can run a duct and will roast hundreds of kilos a week. Choose a drum roaster with a duct. It is proven and, at large volumes, right.

You want to start small and can stand by every batch. A small roaster without built-in cleaning and extraction through a window is the lowest threshold.

You can add a new electrical circuit but not a duct. A ventless machine with an afterburner fits.

You have a normal socket, no duct, and want the machine to roast while you do other things. That is the route we built for. More on it below.

You buy a few kilos a week, or your brewer is on loan from your coffee supplier. Do not roast yourself yet. Keep buying, or have someone contract roast for you.

How we do it ourselves

We roast our own production in Halmstad, Sweden, on a machine we built to pass all eight points above: Science Brewing Roaster.

Science Brewing Roaster on a wooden table next to bags of coffee and a glass jar of green coffee — Science Brewing Roaster with bags of coffee and a jar of green coffee.

Power: Single-phase 230 V, a normal socket on its own 10 A circuit. About 1.8 kW while roasting, up to 2.3 kW while heating up. The current limit can be set from 8 to 16 A. Capacity at 8 A has not been measured yet.
Smoke: Four-stage cleaning: cyclone, water scrubber, HEPA and activated carbon. No afterburner. The water cools the exhaust. Patent pending.
Water: A tank of about 3 litres with a level sensor. The machine and the app tell you when it needs filling. The water is changed when it has turned dark, roughly every tenth roast. More often with dark roasts. No water connection or drain.
Changes to the building: None.
Capacity at 10 A: 1 kg per batch at 10 A, 4 kg an hour. Up to 1.2 kg with certain roast profiles, and up to 2 kg at 16 A (3.6 kW). Theoretical ceiling up to around 100 kg a day.
Staffing: Runs unattended through the batch. You top up beans before every batch, roughly every fifteen minutes, change the water roughly every tenth roast and empty the chaff. With the optional feeder it runs about 10 kg in one go. Safety features in both hardware and software, and the machine alerts you with sound, lights and notifications in the app.
Size and weight: 30 cm wide, 70 cm deep and 40 cm high, about 30 kg.
Outdoors: Yes, at 10 °C or warmer.
Growing: More units, never a chimney.
Help: A food safety plan template for coffee roasteries to download, in Swedish. You get the link with your Space Report.
Price: 6.552 € excluding VAT

If you need more than 300–400 kg of roasted coffee a month there are two routes: more Science Brewing Roasters, or a drum roaster with a duct.

Three ways to take the next step

1. Send a photo of your fuse board and the room

Take the Space Test and reply to the email with your report with a photo of the fuse board and the room where the coffee roaster will stand. We can assess whether a coffee roaster without a chimney will work there, and what you should ask your electrician. It costs nothing. No obligation.

Take the Space Test

2. Taste it first

We send sample coffee roasted on Science Brewing Roaster on request.

Order sample coffee

3. Talk to us

About help assessing your space, or about Science Brewing Roaster. The form is below.

Go to the form

This is not for you if

Your brewing equipment is on loan against volume from your coffee supplier
You pay less than roughly €14 per kilo today
You want to roast in a small room with no ventilation
You need more than 300–400 kg of roasted coffee a month from one machine
You are looking for a coffee roaster for home use

Frequently asked questions

Do you need a chimney to roast coffee?

Most coffee roasters require one. The exception is machines that clean their own smoke, with an afterburner or with filtration and water scrubbing.

Are there other ways than an afterburner to clean smoke?

Yes. Electrostatic filters, water scrubbing, HEPA filters and activated carbon. Afterburners draw the most power. The others draw little power but need the water, filters or carbon changed.

What fuse does a coffee roaster need?

Anything from a normal 10 A circuit to a dedicated 30 A circuit or three-phase. Calculate amps × 230 and add everything else on the same circuit.

Can you roast coffee in a café?

Yes. But bear in mind that a coffee roaster makes noise during some periods of the roast and can give off a smell despite the smoke filtration. It makes the biggest impression in front of your guests, and the machine is built to stand there: enclosed, with a guard on the cooling tray and ON/OFF as the only control. Run a roast in the room before you settle on the spot, and make sure there is enough ventilation. If you have a specific placement in mind, we are happy to help you assess it. Then report the change to the authorities and check your lease.

Do you need an environmental permit to roast coffee?

It depends on the country and the volume. In Sweden, for example, notification is only required above 100 tonnes a year. Ask your local authority.

Can you roast coffee from a normal wall socket?

Yes, with a machine built for it. Expect it to need its own circuit, and check that it has built-in smoke handling.

Can you roast coffee outdoors or at a food truck?

Yes, with a machine that can handle it. Check the socket or the generator, and ask the authorities about registration.

Why is there a visible plume if the smoke is cleaned?

What you see is mostly water vapour, and most of it comes from the green coffee.

Does the room get warm?

Yes. Without a duct, almost all the power stays as heat in a closed room. A 2 kW coffee roaster heats like one radiator, but with good ventilation or an open door to a larger space it can work perfectly well even in a smaller room.

Do I need a sample roaster as well?

It depends on what the sample is for. Which sample roaster a roastery needs, and when none is needed, is covered separately.

Talk to us

Tell us where the coffee roaster will stand and how you buy coffee today. Would you like us to look at your space? Reply to the confirmation email with a photo of the fuse board and the room.

What is it about?

Name and business

Where will the coffee roaster stand?

Have you looked at roasting your own coffee before?

How much coffee do you buy or sell per month?

Do you own your brewing equipment?

What do you pay per kilo of coffee today?

I agree that Science Brewing stores the details and contacts me. Privacy policy

Who we are

Science Brewing exists to end bad coffee. We sell green coffee, build Science Brewing Roaster and a grinder for whole beans.

Ventless coffee roaster: how to tell if your space can handle one

The key points in 30 seconds

It is not the machine that stops your roastery. It is the room.

What is a ventless coffee roaster?

Why do almost all coffee roasteries have a chimney?

Which technologies clean the smoke inside the machine?

Four routes, sorted by what your space needs

The Space Test: eight questions that decide whether your room can handle it

Get your Space Report

What fuse is on the socket?This is where most people fall

Where does the smoke go?

Where does the heat go?

Where does the moisture go?

Where could a fire start, and who is there when it does?

Who smells it and hears the fan?

Do your lease and the planning rules say yes?

What do the authorities say?

Did you pass all eight?

Can you roast coffee outdoors or at a food truck?

Which route is yours?

How we do it ourselves

Three ways to take the next step

1. Send a photo of your fuse board and the room

2. Taste it first

3. Talk to us

This is not for you if

Frequently asked questions

Talk to us

Who we are

We will call you