I've posted before about this topic on other forums --
My wife is ashmatic and has a HUGE problem with formaldehyde outgassing. Formaldehyde is used in carpeting, plywoods, and other wood composite materials mostly to prevent or retard rot. So I'm sure an RV's glues, plywood floors, cabinets, Scamp's rat fur, insulation, etc. is loaded with formaldehyde.
I guess the problem isn't the formaldehyde per se, it's what happens to it when it's exposed to heat. It outgasses into formalin gas (I think). My wife has had severe ashmatic reactions to it in RVs. We went into a new Sunline on a dealers lot (hot sunny day) and she had to exit and use her inhaler. We've been in RVs at RV shows and after going into 4 or 5, she'd start wheezing and has difficulty breathing. I guess its a combination of the amount of formaldehyde, temperature, and the tight enclosed space within the RV that raises the formalin gas concentration levels to such that it creates problems for her.
I've asked questions about it because I don't see how I'd be able to buy a new Casita
at the TX factory with pickup during the summer, and be able to camp with her as we towed it back to VA. I know that as time passes the outgassing decreases. I also know that the best thing to do is close it up in the heat with a ventilator cracked and just let theformaldehyde "cook off" to accelerate the outgassing. I also read that for every 10 degree increase in temperature the outgassing doubles.
Given these factors, although we'd like to buy new, we'll probably look for something used simply because most of the formaldehyde will have outgassed.
For some, the outgassing doesn't pose a problem -- for others like my wife it could be deadly.
She'd also note that the folmaldehyde to hair link for me is well past since I already comb my hair with a damp washcloth... but then ther's the methane problem already alluded to...