Air Filtration Systems

Although ventilation is the most important means against poor air quality indoors, it is often no longer sufficient these days.

Based on our personal experience, the NO2 concentration in outdoor air is already too high in most places to remain healthy in the long term. This is best seen with the example of NO2. While the WHO recommends limit values of 10µg/m³ and studies have already shown health damage above this level, the concentration in most areas of the world is permanently at 40µg/m³ and more. This is true for large cities as well as for rural areas, as air pollutants spread over hundreds of square kilometers. Therefore, in most cases, the best choice is to clean fresh air from outside additionally through special filters.

Unfortunately, we have not yet found a commercially available product that is directly suitable for simple installation at home. Therefore, we have started to put together an appropriate system ourselves from other components.

As soon as we have found the optimal solution for private use, we will publish the necessary components here.

Until then, we can provide the following information:

What is really needed for effective air purification:

  • Fresh air from outside
  • Heat exchanger (Optional)
  • 1st filter stage: HEPA filter for dust (MERV 6 / G4 /EU4 or better)
  • 2nd filter stage: Industrial impregnated activated carbon*) with at least 5cm or 2" layer thickness.
  • 3rd filter stage: HEPA filter for fine dust (MERV15 / F9 / EU9 or better)


  • Never operate an activated carbon filter without a subsequent fine dust filter, as activated carbon emits fine dust.
  • Always use a dust filter before the activated carbon, as its pores will otherwise be clogged by dust in a short time and lose their effectiveness.


*) We are currently testing the exact type of activated carbon that really works. The best so far seems to be a blend of activated carbon from coconut shell, with impregnated activated carbon for NO2 absorption, which is known as XB-17 in the USA.

Types of Activated Carbon

Activated Carbon Fabrics and Meshes

Utterly useless. The filtration performance is barely measurable and is used only for marketing reasons.


Activated Carbon from Wood

Based on our experience, it works for eliminating odors, but too many pollutants remain in the air.


Activated Carbon from Coconut Shells

Filters some pollutants, but not nitrogen oxides.


Impregnated Activated Carbon

With the right impregnation, the NO2 content in the air can be reduced. However, these only filter small amounts of other pollutants.


Mixtures of Coconut Shell and Impregnated Activated Carbon

This type of filter currently seems to us the best activated carbon mixture and is often used in industrial air purification systems and medical products. However, we will test this extensively and then adjust our recommendation accordingly.
In the USA, this type of blend is known as XB-17.



Unlike fine dust filters, which allow less air to pass through over time, the wear of activated carbon is not noticed by the reduced amount of air, but only by the higher pollutant content in the air after the filter. Therefore, it is important to change the activated carbon annually.

NEVER use wet activated carbon. Especially impregnated activated carbon can filter oxygen from the air or release pollutants that were already bound back into the air, if they become wet.

Efficiency of Activated Carbon

The efficiency of activated carbon depends on air temperature, humidity, and airspeed. The basic guidelines are as follows:

  • Air Temperature preferably higher than 21°C / 70°F but not more than 45°C / 113°F.
  • Humidity between 20% - 90%
  • Contact time of the air with the impregnated activated carbon at least 0.3 seconds.

These are only approximate values and can vary depending on the activated carbon used. Pay attention to the manufacturer's specifications for this.

DIY Air Filter (US Version)

This is the first Version of our DIY Air filter.

It consists of components available from Amazon and Delta Adsorbents, which are available in the United States.You can also use products from any other source.

To make it as cheap as possible, we decided to also use the boxes, used for shipping as part of the filter design. So keep all Boxes and use them to build the filter as described.

While you are working with activated carbon, stay in a well ventilated area and use a mask. It will emit fine dust which is not healthy. When you have completed the filter, it will contain a post-filter which protects you from any dust, emitted by the activated carbon.


The way of operation is as follows:

Fresh air from outside is pre-filtered in the first filter box with a FPR5 Filter. This is just to protect the carbon filters from coarse particles and dust.

The second filter srage is the DS 600 Molecular Sieve. This is impregnated carbon with potasium permanganat and reduces several types of Gases or force them to change Molecular structure to something, which is not as harmful or can be filtered in the third filter stage.

The third filter stage is activated Carbon from Coconut Shell. This will reduce or remove most of the harmful mollecules which was able to pass the DS 600 Molecular Sieve.

At this point, there are also all bacteria and viruses filtered from the air. This is why you should not use any UV-Filters in the system. UV-Lamps will create more harmful substances by converting certain molecules to NO2. So avoid UV-Systems at all.

The last filter stage will remove all fine dust, emitted from the coconut shell. Therefore a FPR5 filter is good enough and you do not need any higher filter at that point.

After all that, the fan follows. Use the fan as the last component in the filter system. So if something leaks in your filter system, no air can bypass the filter stages and you can not be exposed to any dust from the carbon filters.

You can use a duct after the fan to lead the air directly to you in the room or into a existing a/c or hvac system.


Note that the highest speed is not always the best for the fan. On lower levels, more harmful Gases are filtered but CO2 will not significantly reduced. On higher levels, u will bring more fresh air into the room but filter performance for certain Gases will decrease. Therefore I recommend let it run on highest level for a few days to get rid of the VOCs and CO2 in the room, then reduse it to 3/4th for better gas filtration. After a few days, you will feel that by yourself how air quality changes with different air speeds especially if you breath the air directly from the duct of the filter.



Shopping List

1pc AC Infinity CLOUDLINE PRO S10 Get it on Amazon

2pc AC Infinity Air Carbon Filter 10" Get it on Amazon

1pc 25 feet - Flexible 10-Inch Aluminum Ducting Get it on Amazon

1pc 8 feet - Flexible 10-Inch Aluminum Ducting Get it on Amazon

2pc Inline Filter Box Get it on Amazon

1pc FPR 5 Filter 14x20x1 from Home Depot or Amazon.

1Cu Ft DS 600 Molecular Sieve Get it on Delta Adsorbents

30Lbs Activated Carbon from Coconut Shell Get it on Delta Adsorbents


Unpack everything and keep the Boxes!

Take the activated Carbon filters from Amazon and remove the screws on the side with the connection for the duct.Remove the cap and use a drill to remove the pins which holds the inner plastic ring in place, so you can remove it.

Remove the activated Carbon, which is used in this filters. We will replace it with two diffferent version you got from Delta Adsorbents. Use the Boxes from the Inline Filter Box to keep the charcoal from those filters for furture use.

Fill one of the filters with the DS 600 Molecular Sieve and one filter with the activated Carbon made from Coconut Shell.

Shake the filter while filling from time to time so everything settels down and to distribute the Carbon within the filter.

Once filled, but back the plastic ring and then the cap. Secure it with the screws.

After that, put those filters back in the box where they was shipped with. Also add the foam it was secured with at the top and bottom. Cut a hole in the top foam to connect it later to the inline filter box.

Close the Box and cut a hole on top too. Use Duct Tape to close any open holes at the box.

Cut 2 vertical holes into the box as shown in our assembly video.

Put the Boxes of the two filters togeter and use duct tape so the air can flow from one box to the other without leaking.

Take the two inline filter Boxes and put them on top of those two filters. U can use the foam from the shipping box and cut holes in those so you can just put the filter boxes on top of the filters.

Make sure the air filters in the filter boxes are unpacked and are facing in the right direction. There is a arrow indicating the airflow. The airflow is from the first filter box to the ds 600 filter, then to the Coconut Shell and then to the second filter box and then through the Fan.

You should replace the filter from the last filter stage with a FPR5 filter from HomeDepot or similar. If you smell at the filter, you will notice that the filter, shipped with the filter boxes are smelling a bit funny and that is why we are using it only as first filter stage, but are recommending replacing it at the last filter stage to a filter which does not smell funny. Because funny smelling things may not be healthy.

Attach the fan with duct tape to the last filter box. Pay attention to the air flow direction of the fan.

Attach the ducts to the filter boxes. You can use one of the foams from the filter boxes to attach one of the ducts to your window from where it can take fresh air.