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Taking Air Samples For Mold Testing: Settle Plate Method

A number of methods can be used to test air for mold or other microbial contamination. One of the oldest methods of testing air for microbial contamination is the settle plates method. Though the method is semi-quantitative, it is still considered a useful method. In industries such as food, pharmaceutical and cosmetics the method is used to assess the likely number of microorganisms depositing onto the product or surface in a given time. The method involves opening and exposing petri dishes containing agar medium suitable for growth of microorganisms of interest. If one is interested in testing for mold, agar plates containing malt extract agar (MEA) supplemented with some antibiotics to suppress bacterial growth would be used. The agar plates are left open at table-top level at selected points in the room for half-hour to 4 hours. This allows mold spores and fragments to settle onto agar media by gravity. Mold test kits (involving growth media) are settle plates.

Settle Plates Results

The number of microorganisms deposited onto the agar surface of the plate over the period of exposure is determined by incubation of the agar plates at 25ºC for 5- 7 days and counting colonies that develop. The results can be expressed as number of colony forming units (CFUs) per unit time. The counted colonies can then be further characterised to genera or species. Higher numbers of CFUs and/or presence of potential pathogenic or toxigenic molds such Aspergillus fumigatus and Stachybotyrs chartarum are indicators of a problem.

Disadvantages of Settle Plates

Settle plate method is an extremely useful method for assessing air contamination by microorganisms. It is easy to conduct and very cost effective. However, only viable microorganisms would be detected by this method and hence it may give a false impression that the air is “clean” if most of the airborne microorgainisms are dead. False negatives may also be obtained from buildings with:

  • very restricted mold growths.
  • very still air in undisturbed rooms.
  • species of poorly culturable molds (e.g., Stachybotrys chartarum).
  • molds consisting of species with poor airborne dissemination (e.g., Aureobasidium on windowsills, Cladosporium on painted cold air vents, Fusarium and many other wet-spored fungi).

Mold Sampling And Identification Methods

Mold Sampling

The mold sampling method one chooses should be determined by the objective of the investigation. One may sample air or surfaces for mold contamination. The standard method for sampling air is to use a volumetric sampler e.g. RCS or Andersen N6 for viable airborne spores and hyphal fragments and Air-O-Cell, VersaTrap, Allergenco and others such cassettes for total spore counts. Testing of surfaces may involve use of RODAC agar plates for smooth surfaces, and swabs and adhesive tape on all other surfaces. It is important to note that adhesive tapes may not work well on wet and porous surfaces. Bulk samples can also be taken and plated onto agar plates or analysed by direct microscopic examination. Dust samples can be collect from surfaces such as carpets, upholstered furniture and textiles.

Media For Mold Sampling

It’s important to select media for mold sampling wisely. If one decides to collect viable air samples, the choice of media to use is very
important. Generally, malt extract agar (MEA) is used. It is a “broad spectrum” medium that supports the growth of a wide range of fungal species. However, antibiotics may have to be incorporated to surpress bacteria growth. Its main disadvantage is that fast growing molds tend to overgrow slow growers making it difficult to count colonies. To overcome this problem, DG18 and Rose Bengal can be used. These media have compounds added to them to slow down fast growing fungi and inhibit bacterial growth. If one is sampling a relatively dry environment, MEA+40% sucrose would be recommended for detecting xerophilic (dry loving) fungi.

Mold Identification

Currently, the only reliable means for routine identification of mold species is to perform traditional mycological methods. This requires years of training and practice. Be sure to use a lab that has a qualified Mycologist on-board (preferably at PhD level). The lab should also be regularly participating in a recognised proficiency testing program such as the AIHA EMPAT program.

Performing Effective Mold Sampling

If you need to take mold samples, use properly trained personnel or to get yourself trained. If you decide to undergo training, select a mold training course that provides skills and background information to enable you recognize indoor mold, develop effective mold sampling strategies, and interpret laboratory results.

Mold Training Course

The unique mold training course is again being offered by MBL. The objective of the mold training course is to provide participants with skills and background information on mold. The course provides insight into the causes of mold growth and control. The training would enable participants to identify mold growth in built environment, be able to decide on the best sampling methods, the types of samples to collect and how to interpret laboratory results. The most common indoor molds such as species of Penicillium, Aspergillus, Fusarium, Trichoderma, Cladosporium, Mucor, Rhizopus, Alternaria and Scopulariopsis and their health effects (where known) are discussed.

For the course details and available dates, please visit http://www.moldbacteria.com/training.html

Testing For Black Mold Growth

Black mold and associated health effects are frequently on the news making the public more concerned about mold health effects. People are worried whenever they see black mold growth either in their home, school or office. We often get questions such as “Is black mold or toxic mold making me sick?” or “How can I tell if black mold in my house is toxic or not?” As we have mentioned before, the colour of mold does not determine whether a mold is a health hazard or not. Not all molds (regardless of colour) are toxigenic or allergenic. The only way to tell if a mold is toxigenic or not is to have it tested by a qualified mycologist (someone who has specialized in mold biology).black mold on ceiling

Health Effects Associated With Black Mold

Some of the illnesses associated with mold growth in homes or offices include:

  • lower respiratory symptoms
  • respiratory infections such as aspergilloses
  • allergic diseases, including allergic asthma and bronchitis
  • non-inflammatory, nonspecific symptoms, such as eye and skin irritation, fatigue, headache, nausea, and vomiting.


An Inexpensive Method to Test if You Are Exposed to Toxic Black Mold or Not

If you see mold growth you may want to have it tested so that you are sure of the type of mold you are dealing with. It doesn’t have to be black mold. Testing for visible mold growth is easy and inexpensive. To have the mold tested you can use the Mold Tape Slide™. The procedure for taking the samples is simple and takes very little time. If you would want to order these tape slides and test the mold growth in your home or office, click Mold Tape Slide™.


Taking mold samples using the MOLD TAPE SLIDE™

Mold Tape Slide

  • Wear suitable gloves. If you are likely to disturb the mold, you should also wear a mask since you don’t want to inhale excessively high amounts of spores.
  • Record the sample number on the slide label. For example:
    • Sample #1 or Tape #1.
  • Peel off seal from slide to expose adhesive (see the words “Peel Here”).
  • Place sticky side of slide onto the surface with visible mold growth and press gently.
  • Place slide back into plastic snap-case (remember you don’t need to replace the seal).
  • Repeat the same procedure for any other sample you wish to take.
  • Once you have taken all the samples, complete the Mold Analysis Request Form.Provide information on where the samples were collected, for example:
    • Tape #1: Basement, west wall
    • Tape #2: Windowsill, kids bedroom
    • Tape #3: Ceiling tile, kitchen
    • Tape #4: Under counter, bathroom.
  • Enclose samples in an envelope for sending by post or courier. Click Mold Testing Laboratory for more details about the Mold Tape Slide™ and for where to send the samples.

Mould Recognition, Control and Remediation Workshop

There is a significant increase in mould-related litigation. As the public and the workforce develop knowledge on this subject, the provision of appropriate information and training relating to mould becomes an integral part of all health and safety programs and is a key component in achieving Due Diligence.

Mold & Bacteria Consulting Laboratories (MBL) Inc. is pleased to present an 8-Hour Mould Recognition, Control and Remediation Workshop.

Who Should Attend Mould Recognition, Control and Remediation Workshop?

  • Home inspectors;
  • General contractors;
  • Cleaning and disaster restoration contractors;
  • Property managers;
  • Industrial hygienists;
  • Environmental consultants;
  • Insurance, financial, and legal professionals who deal with mould issues; and Other professionals or anyone interested in increasing their knowledge or developing their decision-making skills related to indoor mould.

 

 

Mould Recognition, Control and Remediation Workshop Topics:

  • An overview of various types of moulds;
  • How to recognize indoor mould growth;
  • How to develop effective sampling strategies;
  • How to interpret laboratory results;
  • How to perform effective mould remediation.

Click Mould Recognition, Control and Remediation Workshop for details.

Salmonella food poisoning and symptoms

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Legionella pneumophila – Guidelines for Laboratory Interpretation

Legionella pneumophila is a Gram negative, aerobic bacteria that is characterized as an opportunistic pathogen. It is the cause of Legionnaires’ Disease, a severe form of pneumonia and, it is the cause of Pontiac fever, a non-pneumonic form of L. pneumophila infection. Legionella spp.’s mode of transmission is through aerosols or aspiration of contaminated water. The Public Health […]

The Indoor Mold Is An Early Warning Device

The mold (or mould, in the Queen’s English) has been the victim of a bad press. Mention the word and it conjures up an image of something rotting or in the process of decomposition. And yet, were it not for the mold that inspired the discovery of penicillin millions of lives would have been lost. […]