Most people only do half of it

When an air quality warning goes out, people shut the windows and switch on the purifier. That is right, but it is only half the job.

The other half is knowing when outside gets better again. However powerful a purifier is, it only removes particles already indoors. It cannot remove carbon dioxide and it cannot bring in fresh air. A home sealed for three days has low PM2.5 and stale air at the same time.

The catch is that a nose cannot judge outdoor air quality. You are not going to check an air quality website every hour, so what usually happens is that the windows stay shut too long and every genuinely good window of opportunity gets missed.

A balcony is the right place for an outdoor sensor

It is half outdoors, sheltered, and has power — the easiest place to measure outside air honestly. Add the indoor sensor you already have and you can see both numbers at once. Only with that comparison does "should I open or close?" have an answer.

What it did across that day

1. 06:00

   Early morning, clean outside

   Outdoor 20, indoor 18 — much the same. This is one of the best windows of the day for airing out, and the system says so.

2. 08:30

   Commute, outside gets dirty

   Outdoor climbs past 35 and clearly above indoor. The system closes the powered window and starts the purifier. You are on your way to work and do nothing.

3. 11:00

   The worst of the day

   Outdoor approaches 75. Windows stay shut, the purifier runs high, and the indoor line is held under 30.

4. 16:00

   Starting to improve

   Outdoor falls back to the low 40s, but it is still higher than indoors. The system is in no rush to open up and holds the line.

5. 20:00

   The lines cross

   Outdoor drops below indoor. This is the moment that matters. A message arrives: it is cleaner outside now, worth opening up.

6. 22:00

   Aired out

   Twenty minutes of open window clears the stale air and the carbon dioxide with it, and the purifier can drop to low and rest.

Four things it takes care of

Different homes, different approaches

What you need to have

How the whole thing works

Use the ready-made blueprints

The hub ships with 22 tested automation blueprints — think of one as a fill-in-the-blanks form. This mostly uses greenhouse, which exists for comparing numbers, alongside entity_state_trigger_notify for the "you can open up now" message.

Just say the word

You do not have to fill in any of those thresholds by hand. The WOOWTECH hub ships with HA-MCP, which lets AI connect straight into your system, build the rules, and then check for itself that they really fire — so you are not left testing it.

Prompts you can copy straight across

Every block below can be copied whole with the button on the right. Pick the one closest to what you want — you do not need all five.

I have air sensors on the balcony and in the living room. Use them
to work out whether the windows should be open or shut. Run the
purifier when it is dirtier outside, and message me to open up when
outside gets cleaner. Find the devices yourself, and if you cannot
find one, say so rather than guessing.

Set up balcony-based air quality decisions for me. The point is to
compare the outdoor and indoor numbers, not to watch a single
threshold. Before you build anything, be certain which sensor is
outdoor and which is indoor — do not get them the wrong way round.
When the balcony reading is above 35 and higher than the living
room, put the purifier on high and close any powered windows; if I
have none, message me to close them instead. When the balcony
reading is 5 or more below the living room, message me that now is
a good time to air the place out, with both numbers in the message,
and only between 7am and 10pm. Also check the outdoor number at 8am
daily and tell me when it is under 35 that laundry will dry well.
Use the ready-made blueprints on the hub rather than writing your
own. When it is built, test it yourself, confirm it really fires,
and then tell me which devices you used.

We live right on a main road with traffic below all day, so the air
turns bad far faster here than in a quiet street. Tighten the
closing threshold: act as soon as the balcony passes 30, do not wait
for 35. Make the open-up reminder more conservative in return — only
call me when outside is at least 10 below inside, because a gap of a
point or two is not worth opening for. Rush hour is never going to
be good, so do not keep messaging me during those two stretches.

On the balcony air rules, move the closing threshold from 35 to 45.
The purifier sits on high far too much and it is loud, so I want it
starting later. Leave the open-up reminder alone and keep everything
else exactly as it is. Tell me once you have changed it.

Mornings it gets this right. Afternoons it goes odd — from about
two onwards it keeps telling me to shut the windows, and the air
out there smells no worse to me than it did at breakfast. Come at
this from the time angle: split the last week into morning and
afternoon readings and lay them side by side, then check whether
the balcony sensor sits in direct sun by then, or something else
shows up at the same hour daily. Say what you reckon it is, and
leave the settings alone until we have talked it over.

Common questions