I have a species of humanoids that spends a lot of time around fire. They are able to spark their own fires, and they have a reasonable fire resistance. One problem presenting itself is smoke inhalation.

These humanoids are genetically engineered, so evolution isn't a problem. They don't have to worry about poisoning from many substances due to a modified renal system and some helpful bacteria. I am open to any changes, biochemical, etc, as long as they fit within a human shape.

In particular, I am wondering if they could inhale smoke from fire and absorb its components, such as carbon and water vapor, for use in their bodies. What changes to their respiratory system would have to occur? Could they breathe carbon monoxide and carbon dioxide?

Would the use of smoke in their metabolism just be too inconvenient or detrimental to be implemented?


1 Answer 1


Short answer yes you could have a creature that breaths smoke but their blood chemistry will have to be more complex and flexible than what we see in the modern hemoglobic animals. They could absorb Carbon and Water Vapour from the smoke they breath to supplement their metabolism, but there are problems; Carbon Monoxide being the biggest.

If smoke was just Carbon Dioxide and Water Vapour then you'd only need a new chemical in the blood that will scavenge Carbon Dioxide and prevent it from staying bound to the hemoglobin, then break it down, this would be similar to Chlorophyll but use ATP rather than sunlight as an energy source. Water can be pulled directly from the lining of the lungs as it precipitates in them, with a little change in osmotic pressure.

Carbon Monoxide is a problem though; it's chemically different enough from Carbon Dioxide that it doesn't follow the normal metabolic pathways for Oxygen and Carbon Dioxide in the body. Instead it binds to the hemoglobin and doesn't let go, it forms Carboxyhemoglobin instead which can be highly toxic. To have a creature exposed to high levels of Carbon Monoxide on a regular basis you need a different basic carrier chemical instead of Hemoglobin, or a second scavenger enzyme that will preferentially break the Carbon Monoxide out of Carboxyhemoglobin; that's a much larger change in body chemistry.

There is another chemical in smoke that you may wish to consider, if you are burning raw organic material (as opposed to coal or charcoal that have lost most of their Hydrogen) there will be Cyanide in the smoke in low but consistent concentrations. You'll need your creatures to be immune to chronic cyanide poisoning if they're in an environment where growing things are burning on a regular basis.

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    $\begingroup$ In search of an alternative did some quick googling, but it turns out hemocyanin seems to not fair any better with carbon monoxide. $\endgroup$ Oct 14, 2018 at 16:52
  • $\begingroup$ @PinkSweetener Yeah I'm not surprised, carbon monoxide is a weird compound with some really oddball chemistry. $\endgroup$
    – Ash
    Oct 14, 2018 at 17:02

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