The testing of sterilizers. 2. Thermophilic spore papers.

Satisfactory spore preparations for testing hospital sterilizers can be made from B. stearothermophilus and comparatively simple methods for loading and drying the papers are considered to be valid. Each batch of spore papers should be calibrated by plotting dose-response curves for exposure to steam. A minimum standard in terms of the L.D.50 to moist heat is proposed and confidence limits suggested when such papers are used in pairs or small multiples.