Air, Water & Natural Home

The environment you breathe, drink, and sleep in — practical low-tox improvements ranked by impact.

Guides

Evidence: Supported

A Better Sleep Environment: Light, Sound, Temperature, and Air

Your bedroom is a set of physiological signals. Here's how to tune each one, ranked by evidence and cost.

Published Jul 12, 2026

Evidence: Established

Environmental Noise, Sleep, and Health: What the Evidence Actually Says

Noise is one of the best-documented environmental health exposures — and one of the most fixable.

Published Jul 12, 2026

Evidence: Established

Choosing an Air Purifier for Wildfire Smoke (the CADR Math That Matters)

Ignore the marketing page; two numbers — your room's square feet and the unit's smoke CADR — decide whether a purifier will actually keep up.

Published Jul 15, 2026

Evidence: Supported

The CR Box: a ~$70 DIY Air Purifier That Actually Works

Four furnace filters, one box fan, a roll of tape — and EPA chamber-tested performance rivaling purifiers at several times the price.

Published Jul 15, 2026

Evidence: Established

Wildfire Smoke Indoors: What Actually Helps

When the AQI turns orange, most of what protects you happens inside your own four walls — and most of it is cheap.

Published Jul 15, 2026

Related research

Evidence: Established

WHO guidelines identify environmental noise as a significant public-health risk

Guideline · 2018 · European populations exposed to transportation and leisure noise

Chronic exposure to environmental noise above recommended levels is associated with sleep disturbance, annoyance, and increased risk of ischaemic heart disease; WHO issues exposure-limit recommendations for road, rail, aircraft, wind-turbine, and leisure noise.

Evidence: Supported

EPA chamber testing: DIY box-fan air cleaners removed wildfire-smoke particles at rates comparable to commercial purifiers

Mechanistic study · 2022 · No human subjects — simulated wildfire smoke in a large controlled test chamber

Box-fan air cleaners built with MERV-13 filters produced clean-air delivery for smoke-sized particles comparable to commercial portable HEPA purifiers, at a fraction of the purchase price; multi-filter (CR box) designs outperformed single-filter designs, and fan-motor temperature testing found no fire-safety concern with filters attached.

What remains uncertain Every topic on this site has open questions — that's how science works. Individual guides call out specific uncertainties, and our methodology explains how we grade what we publish.