An additive manufacturing apparatus (10) includes (a) a light polymerizable resin unit comprising a surface on which a light polymerizable resin can be supported; (b) a light engine (17) configured to illuminate a region of the light polymerizable resin unit; (c) a carrier platform on which an object can be produced; (d) a drive assembly operatively associated with the carrier platform for advancing said carrier platform (12) and said light polymerizable resin unit away from one another as said object is produced; (e) a purge chamber (300) surrounding at least a portion of said light engine (17); and (f) a purge gas in said purge chamber, or a purge gas supply operatively associated with said purge chamber (300).