Frequent asked questions for Microbial Air Monitoring

1 Which is the microbial principle of the TRIO.BAS air samplers?

The principle is the Anderson according to ISO 14698
  1. A known volume of air is conveyed onto a surface of a culture plate (Petri dish) containing a sterile nutrient medium suitable for the multiplication of microorganisms (bacteria, fungi, yeasts, etc.). The microorganisms present in the air impact on the surface and are retained.
  2. The culture plates are incubated in the laboratory and after 24-72 hours the microorganisms are visible to the naked eye forming the colonies (CFU).
  3. From the number of colonies counted and related to the volume of aspirated air, the environmental hygienic conditions can be assessed for any appropriate corrective actions.

2 Which are the Aspirating heads to be used with TRIO.BAS air samplers?

  1. Stainless steel “ASPI head” (330-331);
  2. Thermopolymer “ASPI (336);
  3. Daily Shift sterile (340-341)

3 How should the TRIO.BAS s/s aspirating head sterilised?

The s/s head should be autoclaved for 20 minutes at 121°C.
The disinfection is obtained by using 70% sterile IPA.

4 How should the body of the TRIO.BAS air sampler disinfected?

In Cleanroom: Wipe the surface with a clean sterile cloth moistened with 70% sterile IPA. In Normal environment: Use a clean cloth moistened with 80% alcohol/deionized water.

5 Are the aspirating heads of TRIO.BAS air samplers interchangeable?

Yes. They are because they are produced under strict control machines. The operator should only check if the holes are dirty.

6 If the holes on Petri dish agar surface are not visible after air sampling, what could be the reasons?

Probably the agar medium is dehydrated. Be sure it is not too old

7 What’s the difference between TRIO.BAS MINI and TRIO.BAS MONO?

MINI is a typical instrument, cheaper, for agro, food, dairy, beverage fields where the use is not very stringent and there is not need of Data Integrity for result registration.

8 At which intervals should TRIO.BAS re-calibrated?

It is suggested a re-calibration after 12 months.

9 When the air sampler says “Calibration expired”, is it possible to continue the sampling cycle?


10 Which TRIO.BAS models can be fixed on tripod?

All TRIO.BAS models can be fixed on a tripod.

11 What’s the reason of calibration reminder message?

When the set time has elapsed, the screen will inform to remind that a re-calibration is necessary

12 Can the holes of the aspirating head get clogged when used in dirty environment?

It can happen. In these circumstances a cleaning with compressed air is suggested.

13 Which culture plates can be used with TRIO.BAS?

Any type of plastic 90 mm Petri dish or 55 mm Contact Plates (RODAC).

14 Is it possible to sterilize the aspiration chamber of TRIO.BAS with VHP?

Yes. It is, following the recommendation of the producer.

15 Is it easy to replace the battery of TRIO.BAS?

You have just to open the bottom of the sampler, disconnect the old battery and connect a new one.

16 What is the max cable length between the command unit and the satellites of TRIO.BAS isolators?

The standard 5 metres can be prolonged up 20 metres.

17 Is it necessary to remove the satellite units during the isolator decontamination by VHP?


18 Is TRIO.BAS creating turbulence in laminar Flow?

TRIO.BAS generates minimal turbulence because the exhaust of the impacted air is in the same direction of the air flow.

19 How are compressed gases tested for microbial contamination?

TRIO.GAS, EASYGAS, FLUGAS are accessories for TRIO.BAS air sampler to monitor the presence of microorganisms in compressed gas.

20 Which compressed gases can be used?

Compressed air, nitrogen, carbon dioxide, argon.

21 What’s the difference between a TRIO.BAS and TRIO.BAS ATEX?

The performances are the same. The TRIO.BAS ATEX model is used for security reasons in potentially explosive atmosphere according the international directives

22 Which are the portable instruments and the stationary instruments?

The portable instruments are included in the yellow line: TRIO.BAS MINI, TRIO.BAS MONO, TRIO.BAS DUO, TRIO.BAS.TRIO, ETC.
The stationary instruments are included in the stainless steel line: TRIO.BAS ISOLATOR, TRIO.BAS MULTIFLEX,1, MULTIFLEX 1+2, TRIO.BAS RABS, TRIO.BAS ISOLATOR

23 Two air samplers of the same model give different result. What could be the reason?

First of all, it is necessary to consider that microbiology is not math and that the microorganisms are not even distributed in the air.
It is necessary to check if the samples were taken at the same conditions and place, if the sampler was decontaminated, if the sampler was calibrated.

24 Which is the more appropriate TRIO.BAS model to choose: 100 or 200 litres of air / minute?

  • TRIO.BAS 100 aspirates 100 litres of air per minute = 1000 litres in 10 minutes
  • TRIO.BAS 200 aspirates 200 litres of air per minute = 1000 litres in 5 minutes
TRIO.BAS 200 is more convenient for Clean Room where the contamination is lower and a higher volume of air should be collected.

25 Which volumes of air are pre-programmed in TRIO.BAS?

32 volumes from 30 to 2000 litres of air

26 Which volume of air should be aspirated?

  • The number of collected C.F.U. on the agar surface, after incubation, should be easily countable (up to 200 C.F.U.).
  • Therefore the most common volumes are 100-300 litres in normal environments (high contamination) and 1000 litres in Clean Room (low contamination).

27 Which volume of agar medium in each culture plate?

14/16 ml in 55 mm Contact plate
24/30 ml in 90 mm Petri dish

28 What is the advantage of battery charger by induction vs traditional cable?

The induction is by contact and therefore there are no connections and cable

29 Why “Interval sampling”?

  • To obtain a representative sample “in operation” conditions.
  • More than one air sample, on the same culture plate, in sequential order.

30 Why “Remote Control”?

Typically it is used in Clean Rooms from the outside of the core to reduce risk of contamination from the operator.

31 Why “Delay Start”?

Typically it is used in Clean Rooms from the outside of the core to reduce risk of contamination from the operator

32 Why to adopt sterile “Daily Shift” aspirating head?

The “Daily Shift” can be used during the complete working shift, all day round.
They have a certification of sterility.
They are used in case of autoclave problems or shift over activity.

33 What’s the difference between “Official Calibration” and “in House monitoring”?

“In House Monitoring” is a test performed by the company staff to control the unit works properly and it is not damaged (e.g.: dropped, mishandles, battery worn out, etc.).
“Official Calibration” is a test performed by a third party to obtain an official document requested by official institutions like the FDA

34 Why and when a statistical table is used for the correction of counted CFU on the culture plate?

If the CFU on a culture plate is very high, there are high probabilities that more microorganisms impacted on the same points of the agar.
For this reason a statistical table (Feller) is used for the correction.

35 Conversion of the counted CFU/plate into CFU/1000 litres of air

Example: Counted colonies in a plate:20 - Volume of sampled air:200 litres Calculation: If 20 C.F.U. in 200 lts = X in 1000 lts 20 x 1000 X=---------------- = 100 C.F.U. per m3 200

36 CFU/ft3 vs CFU /m3

To express the final result in CFU/ft3 or CF/m3 multiply the CFU/litre value by 28,32 or 1000 respectively

37 What is the system for microbial monitoring of flat surfaces?

The flat surfaces are monitored to evaluate the microbial contamination using the CPS System (Contact Plate System).

38 How to write a SOP (Standard Operative Procedure)

A SOP should include: Identification number, Title, Purpose, Glossary, Responsibility, Safety, Standard, Material, Protocol, Non-conformity, Reference.
Several SOP are available on Application Notes

39 Is it possible to record the CFU counted on the agar of culture plate after incubation?

CFU Photo Camera. As requested by Good Laboratory Practice and Data Integrity 21 CFR part 11, the BAS Software records culture plates’ photos immediately before and after the manual CFU count thanks to the CFU Photo Camera (code 337). The CFU Photo Camera is connected to the PC with the BAS Software installed and the two pictures are automatically recorded and saved in the software. It is possible to export all detailed information of a single sample in a pdf file or print a paper copy.

40 Where to find Guidelines for environmental monitoring in aseptic premises.

Guidelines on test methods for environmental monitoring for aseptic dispensing facilities.
Click here to read the guidelines.

41 Where to find Guidelines for Environmental Monitoring according the European Commission.

Draft Guidelines on Good Manufacturing Practice specific to Advanced Therapy Medicinal Products.
Click here to read the guidelines.

42 Where to find guidelines for environmental monitoring in Healthcare facilities

Microbiological Air Sampling of Operating Rooms in Western Australian Healthcare Facilities. Click here to read the guidelines.

43 Where to find WHO Guidelines for indoor air quality : dampness and mould

WHO Guidelines for indoor air quality.
Click here to read the guidelines.

44 Where to find ASM guidelines for Indoor Air Quality

Guidelines for Indoor Air Quality.
Click here to read the guidelines.

45 Where to find WHO Environmental Monitoring of Clean Rooms in Vaccine Manufacturing Facilities Points to consider for manufacturers of human vaccines

WHO Environmental Monitoring of Clean Rooms in Vaccine Manufacturing Facilities.
Points to consider for manufacturers of human vaccines.
Click here to read the document.

46 Where to find CDC guidelines for infection control in Healthcare facilities

CDC Center for Disease Control and Prevention - Guidelines for Environmental Infection Control in Health-Care Facilities.
Click here to read the guidelines.

47 Where to find WHO information on DATA INTEGRITY

Guideline on WHO Data Integrity
Click here to read the guidelines.

48 Where to find FDA information on DATA INTEGRITY

Data Integrity and Compliance - With Drug CGMP Questions and Answers Guidance for Industry.
Click here to read the FDA information.

49 Which is the New European Standard for Cleanrooms and associated controlled environments – Biocontamination control?

It is the European Standard EN17141
Click here to read the standard.

50 Which are the ISO for microbiological horizontal methods for surface using Contact plates and swabs?

ISO 18593:2004
Microbiology of food and animal feeding stuffs — Horizontal methods for sampling techniques from surfaces using contact plates and swabs.

51 Is “BAS SOFTWARE” conform to FDA CFR 21 Part 11?

BAS SOFTWARE for TRIO.BAS microbial air samplers conforms to FDA CFR Reg. 21 Part 11 according electronic records and signature.
The features of “BAS SOFTWARE” are:
  • A login name and password can be attributed to each user.
  • Different software functions are reached by each user according to their profile.
  • Audit trail on all record.
  • Electronic signatures for author authentication.
  • Data and results are saved by user into protected file and for report generation.

52 What’s the difference between Ethyl alcohol and Isopropyl alcohol?

The World Health Organization suggests that 70% ethyl alcohol is superior to isopropyl alcohol against the influenza virus, however, both provide adequate germicidal properties. ... It's widely recognized that ethanol in this concentration is effective against many viruses and bacteria.

Ethanol and isopropyl alcohol are similar small molecules but differ in the location of the alcohol group on their chemical structures. Both alcohols are flammable and both are used as disinfectants.