I've also had a look in the book mentioned above for other possibilities
to
get oxygen at night in my north-facing bedroom - seems as though the
snake
plant might be the one.

Aren't there lots of possibilities? Isn't this to do with crassulacean
acid metabolism (because it was first discovered in the crassulas)
whereby a great many plants in arid regions have adopted a metabolism
that allows them to do their photosynthesis in effect at night, so they
can shut down their stomata during the day and avoid losing water? It's
a long, long time since I read about this.


The book doesn't go into so much detail. It mentions the aloe, snake plant,
orchids and bromeliads as releasing oxygen and absorbing carbon dioxide at
night. Although it does feature a crassula, it doesn't mention the same
properties for it. The snake plant seemed to be the one most suited to a
north-facing room as the others need more light.