Safelights aren’t always safe. They are not safe for all materials, nor are they safe for unlimited time.
Safelight Safety Factor:
not closer than 4 feet.not longer than 4 minutes — 4×4 rule
The chart we use from a 1999 Kodak publication. We have the OA, OC, OO, 1A, 2, 3 10, 13 filters. They can be selected by switch, when needed. The approach we take to using safelights is to limit use. Our lights are located lower than most other darkrooms. The lghts are located lower than work tables, and are directed toward floors.
In addition, we have deep red flashlights for locating items just out of reach on work tables. Even our white lights are low power, or are very narrowly directed for their few purposes. The main use of white light is select, and clean, and make notes; even then, most of our notes are made on the back fo the print, or on recorder.
in the dark, you learn to grope your way, and talk to yourself