[cathodeTubez]

What exactly are in the white fumes from eminated from manganese dioxide reacting with hydrogen dioxdie? Seems hazardous to me.

[AWK]

Search internet for this reaction, estimate thermochemistry of the reaction, and all will be clear.
In fact, this fumes are toxic a bit depending on concentration of H₂O₂ used but with diluted (3 %) you can observe only boiling (less, but still toxic vapors). Why?

[cathodeTubez]

Search internet for this reaction, estimate thermochemistry of the reaction, and all will be clear.
In fact, this fumes are toxic a bit depending on concentration of H₂O₂ used but with diluted (3 %) you can observe only boiling (less, but still toxic vapors). Why?

Because I understand the fume is simply steam and O2 howeverso, I do not know if Manganese slipped into the fumes, thus toxic to inhale the same.

[AWK]

Check boiling point of H₂O₂.

[cathodeTubez]

Check boiling point of H₂O₂.

Excellent detail, nevertheless, its absolutely safe to inhale fume for first few moments (seconds) of fumage. I suppose a thermometer coupled to a buzzer may alert oneself to temperature reaching H2O2 boiling point.

[AWK]

Not exactly. H2O2 wil be always present in fumes. See binary phase diagram of H2O2-H2O system.
What happens with your alveoli when you breathe to much hydrogen peroxide.