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Mold Culturable Air Sampling

Culturable Air Sampling (Andersen or Biocassette™)

Objective

  • To capture and quantify the different culturable fungal spores present in the air.
  • To determine whether the levels present indicate a fungal problem in the indoor locations.

Advantages

  • Culturable sampling allows for the differentiation of Aspergillus and Penicillium, standard speciation of Aspergillus and speciation of other fungi when required.
  • It also provides counts indicative of how many spores are culturable and present in the air.
  • It assesses the viability of many fungi. This can be critical in certain situations when severely immunocompromised people are present.

Disadvantages

  • Culturable sampling methods require that the spores in the air are alive, survive the sampling process, germinate on the sampling media, and compete well with other species present on the growth media.
  • Culturable sampling does not indicate the presence of non-culturable spores, which may also be capable of producing allergies or other irritation.
  • Culturable sampling requires five to seven days for incubation after the sampling has taken place (for malt extract agar, other agars generally take longer).

Equipment

  • Andersen sampler with agar filled petri dishes and sampling pump to draw 28.3 lpm through sampler, or
  • BioCassette™ and sampling pump to draw 28.3 lpm through sampler, or
  • Other culturable air sampler like RCS, SAS, Microflow air sampler, etc., and
  • Calibration equipment as recommended by the sampler manufacturer.

Pump Calibration

Before sampling, always make sure the sampling pump has been calibrated as recommended by the manufacturer. It should be noted that different calibration protocols are adopted depending on the manufacturer and the type of sampling pump used. As an example, Andersen pump should be periodically recalibrated using a dry gas meter to 1 ACFM as follows: (These are subject to change without notification and it is generally recommended to always be sure pumps are calibrated and to follow the manufacturer’s recommendations)

  • Attach a 1” (inner diameter) hose to the inlet nozzle of the sampler and the other end to the outlet of the dry gas meter.
  • Continue to adjust the valve until 1 ACFM of air is being pulled in over a 3 minute test period (use an accurate stop watch).
  • After this is achieved, tighten the lock nut on the adjustment valve.

Sampling Protocols

  • Sampling locations should include problem areas, an indoor non-problem area if available, and at least one representative outdoor area (more are preferred).
  • Air sampling data represent a specific moment in time and so recording other observations are of great importance. Noting items such as weather, activity levels, HVAC operation, and how accessible the outside air is (e.g. nearby windows and doors to the outside) will be helpful in interpreting the results.
  • Sampling at multiple times is often helpful.
Environmental conditions Recommended sampling time @ 28.3 liters/min
Dusty, dirty, visible particles in the air    1 minute
Normal office 2–3 minutes
Very clean indoor areas     4–5 minutes
Hospital settings Call the laboratory

Media

  • A variety of media types are available to suit different sampling objectives.
  • Unless specific fungi are of special concern, the media used should support germination and growth of a wide variety of common fungi.
Media Commonly Used Purpose
Malt Extract Agar (MEA) For isolating a broad-spectrum of indoor and outdoor fungi
Dicholoran-Glycerol Agar (DG-18) For isolating the xerophilic fungi (require low water activity for growth)
Cellulose Agar For isolating cellulose degrading fungi

Shipping

  • Samples should be sent to the laboratory within 24 hours using an overnight courier and packed with care to prevent breakage and contamination.
  • Unless samples will see high heat for an extended time, e.g. stored in a car in the hot summer for several hours, cold packs should not be used.