Iran, Syria, North Korea, and Cuba.
You will put yourself and your company in a lot of troubles if you deal at all even in the simplest business request (including technical stuff) with the above countries.
Thanks, jveritas. Should he report the request to someone?
He was requesting details on how we calculate theoretical efficiencies for mixing ozone and water. Generally, this type of question would be from someone in a water treatment plant. I was unaware that the US forbids trade with Syria (he's apparently from the city of Aleppo). Additional comments are welcome.