Glossary

PFAS are synthetic 'forever chemicals' that resist breaking down and build up in the body, and drinking water is the route you can filter.

Trihalomethanes are disinfection byproducts formed when chlorine reacts with organic matter in source water. They appear in essentially every chlorinated tap.

PM2.5 is airborne particles 2.5 micrometers or smaller, the fine soot and smoke small enough to reach the deep lung and, at the smallest sizes, pass into the bloodstream.

Indoor CO2, carbon dioxide, the gas everyone breathes out, is a marker of how well a room is ventilated. The reading tracks how much fresh outdoor air reaches a room relative to the people breathing in it.

Reverse osmosis, usually shortened to RO, is an under-sink filter that pushes water through a membrane fine enough to strain out dissolved contaminants that a carbon filter misses.

An ERV or HRV is balanced whole-house ventilation, a fan system that swaps stale indoor air for filtered outdoor air while recovering most of the heat and moisture, so ventilating costs little comfort.

mEDI, melanopic equivalent daylight illuminance, is the light measure weighted to the eye's circadian receptor. It captures the blue-wavelength daylight signal your body clock reads, which plain lux misses.

The UV Index is an international scale for sunburn-producing ultraviolet strength, reported as a risk band rather than a vitamin D measure.

UV-B is the ultraviolet band that makes vitamin D in skin and is blocked by ordinary window glass.

Melanopic light is a way of scoring light by how strongly it reaches the eye pathway that tells the body clock whether it is day or night.

Solar noon is the moment the sun reaches its highest point in the sky at a location, rarely exactly 12:00 by the clock.

Photoperiod is the length of the light part of a day, calculated from date and location rather than measured from weather.

Circadian phase is where your internal clock currently sits relative to the outside cycle of day and night.