Free-living adults and pre-adult stages of the scolytids <i>Ips typographus, Pityogenes chalcographus</i> and <i>Tomicus piniperda</i> in bolts were exposed to continuous flows of atmospheres containing carbon dioxide, nitrogen, compressed air, and combinations of the three. <i>P. chalcographus</i> and <i>I. typographus</i> tolerated the atmospheres much better than did <i>T. piniperda</i>. Exposure to atmospheres containing high concentrations of carbon dioxide in combination with low concentrations of oxygen caused the highest mortality in adults: longer exposure times were required to obtain the same mortality in immature stages. -- AATA