I don't know if that was directed at DIY or me, but in the end it doesn't really matter. Overboard on the pest thing? Maybe.. but I tell you what, try paying out nearly $1400 in electricity for a harvest cycle that doesn't ever produce because of spider mites. I hear sooo many stories of bugs hitching rides on your clothes and your buddies clothes.. it just isn't worth it.
I'm not saying I'm always right, but unlike many posters (including alpha.wolf) if I am not absolutely sure of what I am saying then I don't say anything.
To Mr. DIY.. just for the sake of clarity.. the presence of negative pressure (or vacuum as you say) does not mean that no smell is present. This is for two main reasons.. the principal one being that you have to have something exhausting the air OUT in order to have a vaccum, hence a vector for smell dissipation. This is lessened by proper filtering. The 2nd reason, and this is a bigger one; is that the terpines in cannabis (the chemicals responsible for that great smell, are actually volatile organic chemicals (VOC's). So much like other VOC you are familiar with (gas,paint, etc) the smell can passively move through porous surfaces like drywall, wood, etc. Since my room is sealed, this is what I am trying to prevent so I run a single filter as a scrubber.. but only for the last 3-4 weeks.
I'm not actually really worried about smell, I live in a good neighborhood, have friendly neighbors, and I'm in compliance with all state and local medical MJ laws.