The Los Alamos National Laboratory’s latest mask mandate lasted only three days, after which COVID-19 community transmission rates dropped below high, according to a lab memo.

The New Mexico nuclear weapons laboratory let employees take the masks off Nov. 18 after briefly making face coverings mandatory again on Nov. 15, according to an internal email.

Masks are mandatory at DoE facilities in locations with a high rate of community transmission, as defined by the Centers for Disease Control (CDC) and Prevention.

Los Alamos County had a low community transmission rate as of Monday, as did Santa Fe, according to the CDC.

Rio Arriba and Taos counties, near Los Alamos County, had a medium rate of transmission. Another Los Alamos neighbor, Sandoval County, had a high rate of transmission as of Monday.

Bernalillo County, which includes the Sandia National Laboratories in Albuquerque, had a high rate of community transmission as of Monday, according to the CDC.

CDC’s community transmission metric considers both the percentage of new COVID-related hospital admissions and the percentage of staffed hospital beds occupied by COVID patients, based on the weekly average number of new COVID cases for every 100,000 people in a given county or municipality.

This story first appeared in Defense Daily affiliate publication Weapons Complex Morning Briefing.