Parks have been called the “lungs of the city,” by people who really don’t understand the sheer amount of green biomass needed to convert carbon dioxide to oxygen. They figure that having a few trees nearby is enough to provide fresh air to the locals.
Fortunately, parks serve other purposes, so that particular ethos of city design wasn’t completely ridiculous. But what if we were to take that ill-founded concept and scale it down to a personal level? That’s where the Greenhouse Helmet comes in: https://patents.google.com/patent/US4605000A

It’s a simple concept. You put on a giant transparent helmet, you bolt a few flower pots in there, and BOOM: you’ve got a negligible amount of fresh oxygen. Not enough to actually breathe, of course, which is why you have air filters 30 that pass outside air through the helmet.
This design has so many delicious failures. Besides the fact that it’s pointless, the stale air just isn’t going to cycle out fast enough for you to actually survive without some sort of fan to force air through the filters. Second, you’ll look like a literal doorknob. Third, and this is my favorite part, why are they using cacti?? As you can see below, they expect you to go jogging in this thing, so when one of those prickly guys becomes dislodged, you are going to have a pincushion bopping around your face:

You can run from your demons,
but you cannot escape their spines.
Of course, we have been seeing a lot of goofy mask designs lately. If someone had offered me a head-enclosing dome with air filtration in April of 2020, I am not sure I would have said no. I would have taken the cacti out first, though.