Botheju and Bakke (2010) found that rigorous initial aeration of an anaerobic inoculum resulted in a three times longer lag period before gas generation started but also noted a certain reversibility of the inhibition. While details of the reversibility of oxygen inhibition of methanogens remains unknown such an effect was also observed by Gerritse (1990). Zitomer (1998), who conducted experiments under limited oxygenation conditions, reported that the activity was inhibited for a short period (30 min) but methanogens were not irretrievable damaged.