OSB (particle board) does 'out gas' more than plywood. This was an issue with us as we have allergies. WE went with plywood subfloor (more expensive) as well for cabinets (also more expensive). We also added a Heat Recovery Ventilator because it brings in fresh air while exhausting stale indoor air. Of course, we also had to add a large HEPA filter so the fresh air did not contain all the stuff we are allergic to. Then the furnace was upgraded to 2-stage blower so we can run it on low speed 24/7 and insure the house air is exchanged continually. The bath and kitchen ventilators all exhaust outside. We are in the last 2 months of the construction (we hope) so will see soon how all our efforts (and expense) have improved the living conditions for us.
PS: OSB used for exterior sheathing and roofing is outside the 'living envelope' so is not a problem.

[This message has been edited by LDoyle (edited June 28, 2003).]

some contractors put down a plywood subfloor ,then put p-board on top (makes for a quiet floor) p- board if its thick enough can be used as a sub floor ( 1-1/4"),but i would not want one, see if the buget will allow plywood or o.s.b....all wood type subfloors have formaldehyde.good luck