im looking for a gaseous substance (or airborne solid like dust) to use in my story that is organic, has a sweet odor, or at least pleasant enough to not cause any suspicion from main characters, is nontoxic to inhale, has some coloration (whether that be changing the color of a substance it dissolves in, being visible in the air, or having colored condensation), and is combustive enough to explode from some reaction (preferably with oxygen and high pressure/heat) while not active enough to react with other gasses in the atmosphere. one substance i've found that seems close to what i'm looking for is benzene but due to having no coloration and being harmful from prolonged exposure doesn't seem to be quite what i need. thank you! (edit: from what ive been told having all of the features desired but not required isnt possible so please stop saying what i want is impossible and instead just try to have as many as possible, im not looking for all of them im looking for most of them)
Benzene, which has already been mentioned in the comments is colourless. The frequency of light absorbed corresponds to the complementary colour of the colour we see in azo dyes. Benzene only contains a small area of delocalisation, which is not sufficient to lower the energy gap to the visible part of the spectrum, meaning benzene absorbs UV light and is colourless. On the other hand, It has a sweet odour and is highly flammable. Benzene evaporates into the air very quickly. Its vapour is heavier than air and may sink into low-lying areas.
NOTE: benzene may possess a pale yellow colour at room temperature.
Also, though benzene is deadly in case of long-term exposure (Long-term exposure means exposure of a year or more) and causes harmful effects on the bone marrow and can cause a decrease in red blood cells, leading to anaemia, Acute (short-term) inhalation exposure of humans to benzene causes no more than a bit of drowsiness, dizziness or headaches, in relatively lesser concentrations
Given that I am a new member and don't have much reputation, I can't comment on your post, so I am answering here...ozone has a pale bluish colour and also a metallic odour and if it is present in minimal concentration it is not deadly toxic, just might result in chest pain and laboured breathing...In the stratosphere, ozone is formed when a molecule of oxygen absorbs a photon of light with wavelengths shorter than 200nm, is split into atomic oxygen and the atomic oxygen reacts with an oxygen molecule to form ozone, but i am not sure whether it is volatile or not..however, ground-level ozone is formed by reaction betweeen oxides of nitrogen and VOCs (volatile organic compounds)