My memories of my time in high altitude astronomy indicate that there were no oxygen concentration monitors or alarms in the areas that liquid nitrogen was in use at the high altitude astronomical facilities where I had worked.

In high altitude astronomical facilities we routinely discharged large amounts of nitrogen gas into closed spaces. We were never informed by the astronomy management team about the abnormally low oxygen environments that the use of liquid nitrogen creates, how long term exposure to it manifests itself in human health and the resulting abnormal mental behaviors.

When I worked in astronomy, I routinely observed young college and university students working with liquid nitrogen and breathing nitrogen gas as they discharged it into the indoor environment at high altitude.

During my time in high altitude astronomy, I routinely witnessed workers breathing medical oxygen, industrial carbon dioxide, nitrogen and helium gas as part of their daily work routine.

When discharging industrial gas into the indoor environment in high altitude astronomy, we never wore breathing respirators that fed us oxygenated air at above the legally required 19.5% oxygen levels.

Industrial liquid gas containers were left open and venting gas into the indoor environment in high altitude astronomy. On reflection, I realized that I routinely observed mental and physical effects that match those of a low oxygen environment in staff that I supervised.