本文介绍了一种自制空气过滤器的方案，与市售的 Levoit 300 空气过滤器相比，成本仅为其 25%，并且更加静音、模块化，且不受特定滤芯供应商的限制。通过 3D 打印技术和一些现成的组件，例如电脑风扇和电源，即可构建一个高效且经济的空气过滤器。该方案尤其适合动手能力强且对噪音敏感的用户，虽然对于追求时间效率的用户来说，购买成品可能是更好的选择，但这种自制方案提供了一种低成本、可定制的空气净化解决方案。

💨通过结合压力优化的现成部件（电脑风扇）、滤芯和电源，以及使用 3D 打印技术制作适配器，可以自制一个高效且经济的空气过滤器。

💰自制空气过滤器的成本约为每 CFM（立方英尺每分钟）0.45 美元，而市售的 Levoit 300 则约为每 CFM 2 美元，成本显著降低。

🤫自制方案在“非常安静”的运行状态下（约 25 分贝）可实现约 55 CFM 的风量，而 Levoit 300 在最低档位（约 24 分贝）的风量约为 30-50 CFM，且噪音更大。

🔌自制方案不包含任何不必要的智能功能，避免了潜在的隐私和安全风险，用户可以根据自己的需求进行定制和控制。

🛠️该方案具有模块化和可定制的特点，用户可以根据自己的需求选择不同的风扇、滤芯和电源，并且不受特定滤芯供应商的限制。

Published on December 8, 2024 1:47 AM GMT

TLDR: ↓

With access to a 3D printer and some lack of regard for aesthetics, you can build a Levoit 300 (a popular air filter) clone for roughly 25% of the price. 

And against the cheapest possible competition, it is roughly price per volume of air competitive/better but much quieter + modular + not soft vendor locked to their filters.For rich people, the commercial options are better on a time value basis. But what tinkering is a worthy cause in itself.  

Why not just buy n many X filters?

If there is one thing I associate the LW community with, that would be the undying love for Eliezer Yudkowsky and his role as the rightful caliph^[1] Lumenators and Air Filters.

Ever since my allergy diagnosis, I've thought of various schemes to cover my house with the latter. The obvious decision is to acquire as many as IKEA/Levoit/CheapInc. filters as fast and as cheaply per CFM (cubic feet per minute) as possible. Then proceed to plant them around the place and call it a done deal.

Sadly, a quick proof of concept somewhat shattered my dream. After listening to how loud some of these fans are in person, I realized the advertised CFM all correspond to the highest fan setting - and they are very noisy (effectively in the 50~60 db range). And I didn't want to spend hundreds on what are essentially glorified pressure optimized fans on a box. 

Also, I am not the biggest fan of having IoT devices sprinkled in my living quarters - too many of these filters have smart features I don't want. If I didn't write the firmware, I certainly don't want anything with more compute and IO than a Raspberry PI pico controlling my fans and light bulbs.  

Somewhere, somehow, someone must have had this problem and wrote something about it? 

There is an obvious solution

Between "A box taped together with filter as sides and a box fan on top" and "custom designed fan enclosure to win some obscure competition by 0,3% margin", there is a great solution proposed by the BigClive. 

BigClive's solution is elegant. By combining pressure optimized off-the shelf parts (computer fans) with the bare minimal of essentials (the filter itself and a PSU), you can just get a air filter without any of the bells and whistles. And, to free yourself from filter shape vendor lock, if you have access to a 3D printer, you can just print the right sized cone to mount your filter on.

Now, BigClive's solution is not perfect, at least in this specific implementation. The fan he used is not a good fit for the purpose - likely not optimized for high static pressure (even the ones optimized would only get you max 80% of the advertised air flow figures). And the filter itself is quite top heavy and could be pulled off from a simple brush with the cord. But the solution is good.

The shopping list 

For illustrative purposes, here is the pricing in USD at Amazon for the essential parts + some negligible cost in 3d printed plastics. In the perfect scenario, $100 (assuming some tax) gets you 5 mini air filters that each does 55 CFM at around 25 db. All of things above could be had for cheaper. 1 fan does 55 CFM, and 5 does 275 CFM. Assume 80% of the advertised air flow figures, then we have:

For our filter: $0.45 per CFM at "very quiet".

Against the old market leader, Levoit's 300/300s series: 

 Note, the 135 CFM figure is at max volume (at ~60w). If we compare it to the 24 db setting, assuming the cubic root relation between power and flow holds and some extrapolation between the power consumptions at various settings^[2], it is likely to be around 30~50CFM at the lowest setting. Levoit 300 is priced at $100 for the US market before tax and delivery. However, I am sure I am being too generous here because the general anectodal evidence suggest that, even at the lowest setting, the fan is annoying and easily audible, which suggest it to be more 30db ~ 40db range than the claimed 24db. 

At generous reading for the Levoit 300: $2 per CFM at "very quiet".  

How is it working out?

It is working out just fine! Here is the first prototype that I built with a Noctua fan and some other things I had lying around - currently connected to my computer so it would turn on as I turn it on.

 

1. ^{^}

   Obvious Scott Alexander callback here. It is too good to not repeat at least once in a while.

2. ^{^}

   https://www.techgearlab.com/reviews/health-fitness/air-purifier/levoit-core-300 - See When set to medium and used for two hours, the Core 300 used .05 kilowatts. vs an different claim here: https://www.airpurifierfirst.com/review/levoit-core-300/ 

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