labseven

This, and the ergonomics of a lighter pen, is the reason I prefer the capped Pilot Precise BeGreen pen, which accepts the same V5 cartridges. I'm surprised how relatively rare these have stayed when the retractable V5s are everywhere.

Sam Lavigne did a similar project in 2017, generating targeted video ads on twitter.

https://lav.io/projects/the-infinite-campaign/

The two maps I use are purple air and AirNow.gov.

https://www.purpleair.com/map https://www.airnow.gov/

From my understanding, the deep breathing doesn't particularly raise O2 (which is already 97-99%) but purges CO2, which then lets you hold your breath (empty lungs) for 2-3 minutes. In this period, my O2 (on my finger) drops to 85% before I feel a need to breathe in. It is important to 'replenish' the CO2 between deep breathing, otherwise I get very loopy.