ROCHESTER, N.Y. (WROC) — Sometimes, walking outside after a rainstorm, you might find yourself smelling the rain, in a sense. Some people enjoy this specific smell while others do not. But have you ever wondered how this smell is created or if it's even real? Petrichor: The smell of rain According to the American Chemistry Society, "petrichor is the term coined by Australian scientists in 1964 to describe the unique, earthy smell associated with rain." Petrichor is caused by the water from the rain, along with certain compounds, like ozone, goemin and plant oils. The smell of petrichor can be described as "earthy, musky and pleasant." So, what are the things that I'm smelling? Petrichor, or the smell of rain, is caused by a combination of three things: Geosmin Ozone and Lightning Plant Oils Geosmin Raindrops help to release the earthy-smelling chemical called geosmin into the air. The Merck Index, an encyclopedia of chemicals, drugs and biologicals, defines geosmin as the “major volatile component of beet essence, also … the potent earthy odor contaminant of fish, beans, [and] water. The human nose can detect it at concentrations in air as low as 5 [parts per thousand]." Therefore, when rain showers arrive in your area, pollen acts in the same way as these earthy-smelling chemicals, where it is lofted in the air as pollen particles and chemicals. This essentially worsens allergies along with creating the smell of rain. The good news in this process is that the smell of rain we inhale is nontoxic and is not harmful to us. Ozone and Lightning Oxygen molecules are all around us every day. It's how all living that need oxygen to breathe, well breathe. Now, if you were to add lightning and thunderstorms to this component, we then have the splitting of atoms. This process is one of the rare and uncommon reasons why we essentially smell rain showers and is why it's only detectable in the immediate aftermath of a lightning strike. When oxygen molecules are split into individual atoms, they essentially latch on and combine with O2 molecules, making what we called ozone (O3). Although this process is rare and cannot occur with lightning, anytime this does happen, we are left with a distinct smell in the atmosphere. Plant Oils The last contributing factor to the smell of rain is the release of plant oils. During dry periods, stearic acid (a saturated fatty acid with an 18-carbon chain used in skin care and candles), oleic acid (an omega-9 fatty acid that could be found in foods) and palmitic acids (a saturated long-chain fatty acid that is found in most fats and oils) latch on plants and essentially acts as a grease. When there is rain on the way, the odor that is released from these plants gives off a particular smell that we call petrichor. After this process happens and the rain showers move out of the area, the smell weakens by the process of evaporation and the dry of these plants. Typically, the strongest rain smells can be found in wooded areas and fields. Essentially, the more greenery that is around, the more oils and acids area released into the air. Credit: https://sciencenotes.org/petrichor-and-geosmin-the-smell-of-rain/