Submissions and suggestions requested, folks, for that in-universe tome produced by the specialists of the Imperial Exploratory Service, Common Galactic Engineering Practices That Will Kill You .
Specifically, I’m looking for examples of those many fine engineering practices that are routine and harmless for the species that invented them, but which may catch visitors by surprise with something nasty and unexpected. For example, one would be the oxygen-breathers whose blood is based on hemerythrin, which while inefficient compared to hemoglobin, lacks the latter’s great affinity for carbon monoxide. As such, their internal combustion engines that provide auxiliary heat for the cabin tend to do so without the niceties of multiple heat exchangers, and simply vent the exhaust directly into said cabin. Doesn’t bother them, smell aside.
A bit of a bugger for those who assume that “yeah, oxygen atmosphere, we can breathe that”.
Hm. Well, humans (and Earthly mammals generally, I think) don’t have a biological system to detect a lack of oxygen; we detect an excess of CO2. This leads to trouble when humans venture into, say, abandoned vehicles made from iron; the rusting process depletes the air of O2, but since “hey, you’re getting rid of CO2 just fine”, no biological alarms go off.
You could also posit, say, alternative metabolic pathways that aren’t vulnerable to various simple toxins - cyanides disrupt a specific metabolic pathway instead of being generally harmful.
Intense constant or changing magnetic fields could also be a hazard for non-baselines, as opposed to baselines, who generally don’t have large accumulations of metal in them.
As an example, organomercury poisoning seems to hit all eukaryote life (meaning animals, plants, fungi and an assortment of simpler stuff) and some bacteria, but is not only tolerated but actively synthesised by some archaea, like the charmingly named Lokiarchaeota. In fact, the various “Asgard archaea” are suspected to be the major source of methylmercury in the biosphere.
Mercury is a fascinating element with a lot of VERY handy engineering and organic chemistry applications, almost all of which are now forbidden due to inevitably poisoning everything around them. I’m sure life with compatible pathways would make full use of this.
I don’t think it would be deadly, but it could be nasty: humans are actually pretty good at adapting to moderate shifts in external pressure, because we can use our eustachian tubes to equalise our middle ears and everything else can changes sizes or vent in some way. Birds handle pressure changes by having everything connected (eventually) to the nostrils.
But it’s thought some dinosaurs (like sauropods) had additional structural air sacs that weren’t linked to the respiratory system, where changes in gas volume would probably happen via molecules diffusing in and out of their blood. A species like this would probably want to keep a much narrower range of pressures or a much slower rate of air pressure change, and would find the shifts that happen in a human airflight far too sudden and potentially painful.
“…passengers that are buoyant in the cabin atmosphere are reminded that the upcoming six-gee braking burn will result in a commensurate increase in your effective buoyancy, and does not provide sufficient ramp-down time for you to deflate your envelope during the burn and reinflate it after. To avoid harmful interaction with the cabin ceiling, please request for a variable helium-mix bubble to be attached to your seat by our flight attendants…”
I may or may not have been inspired by a certain in-flight mishap of a certain Commercial Resupply mission…