Fentanyl analogues may be hundreds of times more potent than street heroin, and tend to produce significantly more respiratory depression , making it much more dangerous than heroin to users. Fentanyl is used orally, smoked, snorted, or injected. Fentanyl is sometimes sold as heroin or oxycodone , often leading to overdoses. Many fentanyl overdoses are initially classified as heroin overdoses.  The recreational use is not particularly widespread in the EU with the exception of Tallinn, Estonia, where it has largely replaced heroin. Estonia has the highest rate of 3-methylfentanyl overdose deaths in the EU, due to its high rate of recreational use. 
I’ve since tried Snoot’s other type of sprayer, the swivel one, and I highly recommend it over the standard sprayer. It is far easier to manipulate into place and provides a more consistent and fine dispersion. If you look on Amazon, this specific model doesn’t have great reviews, but the ones I have differ in appearance, so I believe they have been redesigned. With the standard sprayer, I would get far more burning, presumably from the larger droplets. With the swivel one, burning is minimized, and I can get the nozzle way up there.