Is watching porn in university a crime?

I am about to start my graduate studies in an American university, moving from my native Peru. Over the course of my under-graduation, I have developed this strange habit of watching porn at odd times, say afternoon, or morning. Sometimes I watch in classroom too, of course, reducing the volume to zero. I ensure I do not disturb others while watching, by not giggling, or engaging in other clumsy activities.

I am nervous about moving to America. Will I be caught by the IT admin of the university and suspended or barred? Does this policy change with universities? Do some universities not mind this? Many of my friends spend their entire nights in their labs and I find it difficult to believe they do not visit any porn sites.

I am teaching a Calculus II session this semester.

The class period is from 2pm to 2:50pm, on Mondays and Wednesdays.

The problem is that my students keep farting while I am going over important theorems and homework problems on the chalkboard.

How can I do something about this?

The smell is horrible; it's like a mixture of hot sulfur mixed in with Chipotle burritos, which I am guessing is what many of them are eating before attending my class. (We have a Chipotle nearby.)

I am afraid to speak up, yet I see no plan of action that would get the point across to my disrespectful students.

What would YOU do?