Mold Sampling

Mold Sampling

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Mold Sampling

Mold Sampling

There are a variety of means to conduct sampling. Viable, nonviable, bulk, swab, tape, and scraped samples are physical samples. Water samples typically test for bacteria levels due, for example, to sewage influx. The final category are air samples.

  • Viable Samples are samples of live mold that can be grown in a culture plate usualy on a potato dextrose agar and it normally taken 1-1.5 weeks to complete this process.
  • Nonviable samples are those that cannot be grown into colony forming units and this process of lab analysis usually takes between 1-3 days to complete.
  • Bulk samples are typically a 2 x 2 inch piece of material with mold growing on it that is cut from its surroundings.
  • Tape samples are a tapelike sticky material that is pressed onto the surface of the visible mold and then onto a plate for microscopy.
  • Swab samples use a Q-tip like instrument to swab against the visible mold. The moldy swap sample is placed in a test tube like instrument and sent to the lab for analysis.
  • Scrape samples are literally scrape from the moldy material and bagged and properly labeled for lab analysis.
  • Air Samples consist of three basic impaction mediums: culture plate (usually potato dextrose), standard impact,  and cassette impaction. These will help determine the level of bio-aerosols
  • It is important to note that it is always advisable to take both an outdoor and an indoor air pre remediation and post remediation to have a comparative basis to analyze regarding project closure.

Why Sample?

It is important to take mold samples for a variety of reasons. Firstly, mold spores are not visible to the human eye. Only by laboratory analysis can one know what types of mold exist in a building. Lab analysis will provide evidence of the size and scope of the problem in a building and based on the type of sampling conducted provide a list of the types of mold present in a particular area. By knowing what types of mold are present, the remediator will also based on knowledge now the health effects associated with the particular types of mold and be able to take the proper PPE, lack of occupancy, and containment precautions

Types of Samples

  • Please refer to the above section.


Viable vs. Non-Viable

Nonviable and viable spores of a certain species look the same. All spores can cause allergic reactions in people. Nonviable spores are those that cannot be grown. For whatever reason, for example, poor spore growth conditions such as insufficient moisture in sporation, these spores cannot be grown on a culture plate. The majority of spores are nonviable.

Viable spores, unlike non viable, can be grown on a culture plate and can be speciated in the lab. The lab usually sends back a report that identifies the type of mold, and the number of colony forming units (CFUs) identified.

The advantages of viable sampling are that the  genus and species can be identified and you will be given actual cfu numbers that can be used for comparation analysis. Viable sampling is popular, accurate, and widely accepted. it does take longe to process-about a week +/- a few days.Samples have to be judiciously selected, the sampling equipment must be purchased/rented from a lab for a fee, and the properly labeled samples must be overnighted back to the lab in a cooler.

The advantages of non viable samples are that they can be quickly and easily identified by microscopic appearance, size, and shape in just a few days or less. It is less expensive and involves simpler testing kits without special S & H requirements. However, nonviable sample testing will only identify genus. Professional preferences lean toward viable sampling.


Bulk and Surface Samples

Physical non air based samples are called surface and bulk samples. Both surace and air sampling kits can be ordered from your lab of choice. Be sure to order these sufficiently prior to your testing date to allow time for shipping and handling.  These samples are bulk, tape, swab, and microvacuum samples. What is a bulk samples? A bulk sample is a physical piece of material with actual or suspected mold growth. Bulk samples are always cut or removed in a consistent size, typically 2 in. x 2 in. This sample is then bagged and properly labeled for chain of custody and sent to the lab. The lab will then measure a set size of the sample and plate it onto a Petri dish (commonly a potato dextrose base) for growth and analysis purposes. Bulk sample results are in a cfu.cm2 format. Swab samples are taken using a Q-tip like swab. This swab is rubbed against the area or suspected or visible mold growth, placed in the test tube, labeled for chain of custody, and sent to the lab. Microvacuum samples use a slitted ampling cassette that has a sticky substance. It is placed just above the surface, turned on, and the spores on the surface are drawn up and impact the sticky material. The lab performs a microscopic analysis in the cfu/cm2 format. Tape samples are another type of surface sample. A sticky piece of a tape like substance is applied directly to the surface to be tested for actual or possible mold growth. The lab will perform a microscopic analysis. This type of sample will determine what types of mold or fungus are present on that surface.


Air Samples

 Air samples are conducted in two manners. The first means is by having the air sampling equipment impact the incoming spores onto a culture plate. The lab is able to count colony forming units (CFUs) that grow because the amount of air entering the testing apparatus is known and the lab then uses a formula to calculate the cfus per cubic meter of air. A culture sample allows for the identification of genus and species. The second air sampling method is using a sticky medium. The air borne spores directly impact this sticky medium. This method also allows a spore count and genus identification per cubic meter of air. Sticky impaction counts all spores, viable and nonviable unlike culture plating which only counts viable mold. Bacteria is usually taken via water samples and is grown in a culture plate (not sticky impaction method) to identify the type(s) of bacteria and any associated toxins. Waterborne bacterium commonly tested for are E. coli and Legionella.  Remember that mold can cause health problems. Mycelial fragments and nonviable mold can still be allergenic.


Sampling Plans

What is a mold sampling plan? A sampling plan is a plan of why, when, where, and how the mold tester plans on taking specific types and numbers of samples to test his/her hypothesis. A thorough sampling plan includes area of suspected growth, suspected levels, and a range of materials to be sampled. It should also detail why and how each sample will be taken. A list of materials and areas to be sampled using a variety of sampling methods is good practice. A list of the date, time, place and operating parameters of all samples if also necessary. Before and after photos in areas of suspected or actual mold growth and in pre and post remediation areas is also solid practice. It is recommended that a combination of air and surface sampling be conducted. Air sampling should be conducted a this is a means of comparative analysis to culmination mold remediation projects. Some companies specialize in designing sampling plans. A good sampling plan should help answer your questions or hypothesis about a suspected or actual mold problem and will form the basis for how the mold remediation plan is developed and conducted.


Laboratory Analysis

 The laboratory conducts the actual analysis of the samples via microscopy, genus /species identification as possible, culturing, and cfu counts and then provides the results to the originator.

 The lab results from the samples comprise some of the most important data in a mold remediation project. Once the lab reports are sent to the originator, the lab results should be summarized whether in written or chart format. A trend analysis on the data should be conducted. This could include but is not limited to looking for common species across rooms located close to each other and connected by vents, molds more common in waterlogged properties, precursor species, or molds with carcinogenic effects. An examination of levels in the various sample zones should be conducted. The question was is similar and what is difference should be posed.


Data Interpretation

 The data interpretation phase is an assessment of the information collected during the walk through investigation of the property, use of the property, the examination of the lab results, and knowledge of various molds and their health effects. How the facility is used, the health status of occupants, and physical state of the facility will all impact how the remediation plan is designed; for example, will occupants have to be relocated temporarily?A problem can exist at times even in the absence of conclusive lab results. Experience and training must also be relied upon, not just solely lab results. Then the following questions must be answered and defined. What mold(s) do the lab results identify, where is/are the mold(s) located, and what are the mold exposure levels? Are there significant enough levels in specific areas that will require occupants, particularly immuno-suppressed individuals to relocate during the project. When are where will they be relocated to. Often this requires a meeting with the business manager(s) and adequate planned alternatives. The source of the moisture problem must be structurally corrected or mold may recur. There should also be an analysis as to whether any human symptoms or complaints are causally linked to the mold problem. The remediation company would have knowledge of molds and their associated health concerns

 Once the source of the water intrusion(s) are identified, the structural repairs can be made prior to remediation. Then the actual remediation plan can be implemented and post mold remediation testing and  the project closure process implemented.


Post Remediation

In having set your mold remediation goals, you would have set acceptable spore levels. Note that post remediation sampling analysis guidelines allow for some amounts of mold spores. A comparison of pre and post mold remediation samples is important to assess the spore level reductions and to assess how well the goal(s) is met to close the project.

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