BS ISO 16000-36:2018 pdf download – Indoor air Part 36: Standard method for assessing the reduction rate of culturable airborne bacteria by air purifiers using a test chamber 6.1 Preparation and maintenance of stock culture Rehydrate the lyophilised reference culture of the test bacteria according to the manufacturer’s instructions. Transfer the rehydrated reference culture to a conical flask containing a defined volume of nutrient broth medium (5.2.2.2). Incubate for (18 ± 2) h at (36 ± 2) °C in an incubator (5.1.6) while gently shaking. Add the same volume of 20 % (volume fraction) sterile glycerol or 10 % (volume fraction) dimethylsulphur oxide (DMSO), to the bacterial suspension to attain 10 % (volume fraction) glycerol or 5 % (volume fraction) DMSO suspension and mix well. Distribute the aliquots into plastic tubes of approximately 0,5 ml and store at (−70 ± 10) °C in a cryogenic freezer (5.1.7) for a maximum of two years. 6.2 Preparation and maintenance of working cultures of the test bacteria on agar plates Prepare a working culture of the test bacteria from the stock culture (6.1). Equilibrate the frozen stock culture to room temperature (15 to 30) °C and inoculate the bacterial suspension to a nutrient agar plate (5.2.2.3) in such a way that single colonies are obtained. After cultivation, store the plates at (5 ± 3) °C for not longer than one month. 6.3 Preparation of working culture suspensions Inoculate (50 ± 5) ml of nutrient broth media (5.2.2.2) in a conical flask of 300 ml with one to five colonies from the working culture agar plates (6.2) and incubate for (18 ± 2) h at (36 ± 2) °C while gently shaking. Obtain a concentration of about 1,0 to 3,2 × 10 3 cfu/ml (equivalent to 300 “full holes” in a 300 impactor lid, if 100 l were impinged) for testing. If the concentration of the test bacterial suspension is more than 1,0 to 3,2 × 10 3 cfu/ml, dilute this suspension with physical saline solution (5.2.2.4) through 10‑fold dilutions. Store the culture suspension at (5 ± 3) °C and use within 4 h. To test the concentration of the bacteria in the suspension, inoculate the prepared suspension on nutrient agar media through 10‑fold dilutions and, after incubating at (36 ± 2) °C for (18 to 24) h, count the colonies on the plates. 7 Procedures 7.1 General Prevent any bacterial contamination by preparing...
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