Are you feeling the petrol odor just looking at the picture? I do. As if I am inhaling it right now and a magic chain reaction starts: one deep breath and a gulp of air rushes up the nose carrying tiny molecules right to the receptors sending an electrical signal to the nerve cells and further to the olfactory bulb, finally reaching its destination - the part of the brain that is not only responsible for smell identification but operates our emotions and memories and... What happens at this point with you in particular and why, well, it depends as we all react differently, some of us enjoy the aroma others don't and there are many reasons for that. This is the general workflow of smelling as we know.
Just to make it clear from the beginning, inhaling any chemicals is not healthy and never should be done on purpose and as much avoided in any situation as it is harmful to human health and may cause serious damage.
There are several theories that explain mechanism of smelling, one, more classic and widely used is based on a chemical view, it states that the aroma recognition depends on molecule shape, size and it's functional group. It means that to feel a particular smell specifically shaped molecules have to take place in specifically shaped receptor slots pretty much making a certain figure, it is called the "Shape" theory of olfaction. It has one major flaw though, some identical shapes make different fragrances. This can be explained by another theory - "Vibration" theory, it is considered to be controversial as according to it the smell perception depends on the vibrational frequency of the molecules in the infrared range. It deals with the different scents when shapes are the same but this theory also has weak points, some substances like helium are mono-atomic and have no structural vibrations and thus have no smell but some have no smell despite having structural vibrations. It is possible that our nose covers only some ranges of frequencies but not all, it is not yet proved. Scientists are still working on these theories and others conducting multiple experiments in genetics, biochemistry, physics and all of them with contradictory results without any clear outcome. It is a circus, really :)
But these theories only aim to explain the mechanism of smelling and recognition but not our reaction to it. In our everyday life, we are surrounded by different scents, sunlit meadow smells of grass and wildflowers, freshly baked bread feels warm and cozy, a fragrance of the loved one makes you happy and strong petrol fume does not really fit in this picture, does it?Personally, I enjoy the light scent of petrol though it is only second in my chart of favorite chemical smells. The one I enjoy most is creosote, it always has been the first and I am pretty sure it will always be. Petrol is, obviously, not the nicest odorant, it is so different from the pleasant ones we all tend to like, so what makes the petrol smell so tantalizing?
Olfactory sense is vital not only for survival as it helps to detect danger such as poisonous gas, for example, but also to select proper mates and find food just like in the animal world. Humans are able to distinct trillion of scents (it was actually believed that only around 10 000 but recent experiments show that this number is too low) but how we perceive the same smell may depend on a lot of factors - time of the day, weather, hunger, mood, sickness etc. Also, different people feel the same scent differently.
It may be so that we are not born with any preferences but there are factors that influence the perception of some of the smells as dangerous, strong and irritating, for example. Overall the like or not like attitude is psychological and depends on every individual's experience with a specific smell. My love for creosote can be explained by happy childhood memories, perhaps it started with my first ever travel to the seaside when I was about three years old as since that trip my Mom recalls that she started taking me to railway stations because I asked to go "smell trains". Whenever I sense the creosote I feel a light excitement and I breath more deeply as it is truly enjoyable to me. I also like the petrol smell but I know people who feel really sick because of it and even may throw up when sensing it for too long, this may not be a psychological thing but some individual physical intolerance though.
At this point, it is important not to mix up the random pleasant encounters with inhalation abuse. Petrol itself is a known intoxicant that produces a variety of short-term effects like feeling of excitement and euphoria when inhaled, it may last from a couple of minutes to an hour but after -effects can be much less pleasant - dizziness, nausea, shortness of breath, indigestion, chest pain, hallucinations, muscle weakness, loss of motor coordination and slowed reflexes. Petrol is a solvent so long term effects may lead to internal organ damage. It does not mean that when filling up your car or a motorcycle you need to hold your breath, it is not the same as sniffing, huffing or bagging for pleasure that is considered harmful, just be careful and you will be fine.
So, do you like the petrol smell or maybe you've got other preferences? Does any memory come to mind when you hear any particular smell?