sealing small openings into living area from crawlspace

Hello My crawlspace is pretty smelly- there doesnt seem to be any visible mold but there is plenty of efflosescence. I also noticed some water on the vapor barrier. I am looking into various ways of dealing with the problem and want to do the right thing. But till then I have noticed a number of openings a) between the interiors wall and the stairs that run over the crawlspace b) the heating returns metal and the dry wall. c) the edge of the floor boards and the banisters for the stairs. I have a vapor barrier on the floor boards and laminate flooring, but some of the smell seeps in through the edges.
a lot of the smell of the crawlspace comes in from there. The heating ducts run through the crawlspace and when its on the whole house smells like the crawlspace - so I dont turn on the forced air at all.
How would you recommend to seal these openings ?
Thanks
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Caulk the small openings for the most part, expanding foam for bigger voids and (real ASTM rated) duct tape on the sheet metal to prevent air exchange with the HVAC. I assume air is sucked in the returns as the output ducts would be under pressure WRT the crawlspace and vent outward.
Also make sure the crawlspace itself is properly ventilated. Sometimes people pile stuff outside their homes that impeed airflow into the vents on the perimiter of the house. An active fan in this area (on one or more vent openings) will accelerate the drying and abate the smell it appears to me. A few hours running an ozone generator in the crawlspace might also reduce the smell if it is a mold. If you have condensation on the vapor barrior, it is a safe bet ventilation is insufficient.
A carbon (charcloal ) filter on the HVAC might also help with the smell.

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A quick sealent that I like to use is GreatStuff(tm). You do want to get rid of the moisture first but if there are signs of mold it may be a good idea to look into getting an in-home fungiside agent to prevent further damage.
HVF
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Check out the information at http://www.advancedenergy.org/buildings/knowledge_library/crawl_spaces /
I sealed my crawl space per Advance Energy advice you'll find at their web site and placed a de-humidifier in the crawl space. Took the smell completely away.

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