2 Research
Before I buy or model anything, I need to know what the filter is up against and what each part of it has to do. The plan lists the questions. This post sorts them into topics, in the order I'll answer them, and says how I'll answer them.
The order
The topics depend on each other, so the order matters. The smell decides the filter media. The media and the particle filter set the resistance to the air. The resistance and the airflow decide the fan, and the fan decides the noise. The sensors come last, because they have to measure whether all of that works.
The topics
| Topic | Questions | Decides |
|---|---|---|
| 2.1 The smell and the filter media | What's in the smell from urine and from faeces. Which media catch which part of it, how much media it takes, and whether the baffles help. | The gas filter section of the case |
| 2.2 The particle filter | Which HEPA grade, or whether a lower grade does the job with less resistance. A panel or a sheet cut to size. A pre-filter for cat hair. | The particle section, and part of the fan's load |
| 2.3 The fan | The airflow through the whole filter stack, not in free air. Static pressure and noise. A 12 V PWM fan with a tach output, axial or a blower. | The fan, and the shape of the case around it |
| 2.4 The sensors | Which readings are worth having: PM2.5, VOC, temperature and humidity, ammonia, and the pressure across the filters. What each one can and can't tell me. | The electronics, and how I'll know the filter works |
| 2.5 Sourcing | Where to buy each medium in small amounts in the UK, with a data sheet. FÖRNUFTIG's filters, as something to compare against. | What I can actually build |
Each topic gets its own post, numbered 2.1, 2.2 and so on as I get to it.
How I'm doing it
AI does the reading. I give ChatGPT one topic and the plan post as its brief, on the Pro setting, and it searches papers, manufacturers' data sheets and government guidance. The first topic took it about 16 minutes.
Then it gets checked. ChatGPT can be wrong, and it can be wrong about a number while sounding sure of it. Before a topic goes into a post, Claude reads the sources ChatGPT cites and checks the claims that decide something against them, and the post says which claims were checked and what the check found. The full answer goes into the project's repo as source data, so I can go back to it later.
Research only gives me candidates. The room decides. The sensor baseline from the plan still comes first, and every choice the research points to gets tested in the room against that baseline.