It's called a professional cleaning.

mrsconn23

Dear Prudence, 
My parents are getting ready to sell the house my brother and I grew up in, and my brother (now 21) is living in the basement while working and saving up for his own place. For the past five years, he has been smoking pot in the basement. A lot. When I was home from college during the summer, I smelled it all the time, and I still smell it when I visit. My parents have turned a blind nose to this, which has resulted in the entire basement smelling like stale pot smoke. How can I tell them, nicely, that there’s no way they will sell the house until they do something about the disgusting smell coming from the basement?

—Basement-Dweller Smeller

banana468

She may not need to tell them.   When a realtor does a walk through and wonders if they're hoping to sell the house to Dead Heads or Phish fans Mom and Dad should get the point.

When my IL's sold their house their realtor told my FIL that his desk needed to be cleaned.   Anyone worth his/her salt will say that offensive smells must go. 

scrunchythief

At least in my area, there are also cleaners that specialize in cleaning to move out/sell a house.  She could suggest that, just in general.

charlotte989875

As someone who just walked through about 30 houses in three days, the LW is right, people will notice. Get it professionally cleaned. 

princessleia22

Ozium works wonders on tough smells. We used it to get cigarette smell out of DH's old apartment when we moved out.  We also bleached the walls to get the nicotine stains out (it was SO disgusting).  He had been in that apartment 8 years.  We actually looked into hiring a professional service that uses an ozone machine to eliminate odors.

Getting smell out of basement would be tough though, because you may not be able to get air flow through their to really clean it out.

ShesSoCold

charlotte989875 said:

As someone who just walked through about 30 houses in three days, the LW is right, people will notice. Get it professionally cleaned. 

H and I looked at 41 houses total. The other day he said something about the "house with the tore up bathroom and swamp in the backyard". I had NO IDEA which house he was talking about until he said "with the dog piss".

A half demolished bathroom (literally - no drywall, toilet not hooked up) didn't stand out nearly as much as the smell of dog urine in the basement.

MesmrEwe

A professional cleaner is a good idea even if the house was in perfect OCD house clean...