Question: What happens if I inhale too much formaldehyde?

There is an overview of some of they symptoms of formaldehyde exposure over on the OSHA website, here:

https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.1048AppC Interesting bit under the part about inhalation is that while it does trigger a range of acute symptoms (all the way from airway irritation to death), folks who have developed a tolerance (which can kick in over the course of a few hours) may not experience noticeable symptoms, even if their exposure to more dangerous levels of formaldehyde has increased.

The OSHA sheet also covers chronic respiratory issues that can develop with longer-term exposure.

From /wiki/formaldehyde:

Symptoms of exposure to low concentrations of formaldehyde may include headache, nausea, throat and skin irritation, and exacerbated chemical sensitivity. For a quick summary of formaldehyde exposure basics, please see the ASTDR’s ToxFAQs for Formaldehyde. For much more in-depth information, please see the ASTDR’s Toxicological Profile for Formaldehyde.