Smoking violation / tenant security deposit (Massachusetts)

[Marc V Palmeri]

Hi,

I have tenants that are ignoring the no smoking addendum in their lease and smoking both weed and cigarettes in their unit daily.  So far I've only communicated via text or face-to-face that they are violating their lease, but they are still doing so and just trying to hide the smell.  My question is, is there anything more I need to do to (i.e. issue a formal written notice of lease violation) in order to prepare for the possibility of keeping a portion of their security deposit to pay for eliminating the odor?  I've read up on local (Massachusetts) law/guidelines regarding utilization of security deposit but it's pretty vague in this regard.  I'd imagine this falls into the "normal wear and tear" category but I just don't know how you measure or prove it and how much tangible evidence I need to have ready showing that I've warned them repeatedly.  

thanks,

Marc