How to clean air indoors

Question

What is the best way to clean indoor air the lifehacker way?

That is, excluding store-bought air purifiers of expensive brands.

Something like DIY: Building an energy efficient and low cost filter would count if construction plans/ideas and maintenance costs were to be considered.

It's mainly about particles and dust from burning candles, incense, tobacco, but also the usual dirt and inner city pollution from roads and vehicles, humans, pets, pollen. Some of that is not easily avoided. Odours are much less of a concern.

Vacuum cleaners with good filters should be considered a given. But they use huge a mounts of electricity if left turned on for long, just cleaning the air and not only carpets.

Structural alterations like plastering the walls of an apartment are not feasible.

Plants are nice and effective according to NASA, but already present and not really cutting it.

Answer 1

A 50 cm (20 in) cardboard-framed air filter, availblef for ~US$3, is the size of many box fans. Though electret filters are more efficient at trapping particles, I find they impede airflow too much and use coarser fiberglass filters. It helps particularly in pollen season.

To help keep it in place when the fan is off, I use a length of cord tied to a rubber band to make a loop. Suction holds the filter when the fan is running.

Answer 2

The particles you're worried about are too small to be trapped by an improvised filter. A vacuum cleaner won't trap these either. You really need a purpose-made HEPA filter as used in air purifiers and the like.
You can buy a HEPA filter (usually as a cartridge to be used in an air purifier) and attach it to the intake of a cheap fan. The attachment should be airtight. Duct tape is an option, or you can build a wooden box with a slot for the filter at one side and e.g. a bathroom extractor fan at the other side.

But the most cost-effective way to improve indoor air quality is to stop smoking.