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Wondering if that musty smell in your home or office is mold?

mold inspectors under a building in material hazard suits testing for mold

Mold Testing – Mold Inspection

Performing a mold inspection or mold testing in the Bay Area is very important if there has been any leaks or a flood in your building, or there is a “musty smell” emanating from one part of the building. It is important to determine if there is an indoor source of mold and a thorough test and inspection will do just that.

An expert should not sell testing without a thorough moisture and mold inspection. In fact, sometimes mold testing is a bad idea and could be a waste of money.

Other times assessments must include lab analysis in order to identify the notorious “toxic black mold,” Stachybotrys, or to determine what parts of the building have been cross-contaminated with mold spores during remediation, or to determine if an area within containment has been properly cleaned during an abbreviated survey known as “mold clearance testing.”


mold growing on building interior ceiling - mold testing San Francisco Bay Area

Mold testing and mold air quality test is an art and science Experts do not always recommend spending money and time on testing. But there is a time and a place for strategic sampling plans.


Any qualified environmental consultant or industrial hygienist will confirm that a mold inspection is a top priority, especially in the Bay Area, where mold and moisture are prevalent. By using a flashlight, IR camera and moisture meter, two eyes and a nose, a good mold inspector can usually tell you whether mold is present, and often he or she can draw conclusions as to whether it could be toxic. Sampling in the absence of a thorough moisture and mold inspection is not recommended, and the data collected from such sampling is missing context and next to meaningless.

Healthy Building Science advocates the following steps:

  1. A qualified, professional expert should provide a thorough moisture and mold inspection of the building.
  2. Formulate hypothesis as to the presence of moisture, sources of moisture, and the extent of mold damage.
  3. Determine if sampling would add value to the mold assessment, or not (skip to #6, if not).
  4. Develop a sampling plan to test the hypothesis.
  5. Sample and review data.
  6. Report on findings from inspection, hypothesis developed, sampling results, and conclusion for next steps.

If your mold inspector doesn’t offer a comprehensive moisture assessment, pushes a lot of testing, or does microbial testing and only shares the lab results without a clear interpretation of their meaning, they are not providing value or helping your cause. Unfortunately, the do-it-yourself petri-dish style mold testers are equally worthless in the absence of a professional inspection.

Mold testing is useful for:

    1. Determining relative toxicity of mold species in presence of symptoms or sensitive populations.
    2. Establishing a baseline prior to remediation.
    3. Determining the scope of contamination.
    4. Clearance testing after remediation to confirm the area is clean, and, last but not least,
    5. Peace of mind for those really concerned.

    Testing Methods and Strategies for Mold

    Most environmental consultants will perform a survey that includes some form of microbial lab analysis. Like testing for any pollutant, there myriad ways to collect samples and have them analyzed in the lab.

    Here are a few of the more common testing methods:


    • Spore trap

      A known amount of air is drawn over a greased slide. The slide is analyzed by a lab technician who can extrapolate a “spore per cubic meter” number for each sample. Spores can be identified to the genus level, but not to the species level. Penicillium and Aspergillus cannot be distinguished between each other in this microscopic analysis. Comparing indoor samples to other samples from outdoors and elsewhere indoors can help draw conclusions about a building.

    • Bulk mold testing

      A tape lift or swap or bulk building material such as a small sample of drywall can be analyzed through a microscope. This method has the same limitations as a spore trap.

    • Environmental Relative Moldiness Index (ERMI) or Polymerase Chain Reaction (PCR)

      This method utilizes microbial DNA analysis to identify species level, but only a relatively few species have been cataloged so unfortunately, this rapid testing method can miss the majority of molds present. Many environmental doctors and naturopaths are familiar with this method and it has gained more traction in recent years.

    • Mold Culturing

      Viable mold spores can be sent to a testing lab to be cultured. The spores are placed on Petri dishes with a selected growing medium, sufficient moisture is provided and the temperatures are regulated to simulate optimal growing conditions. Some spores may be present (and toxigenic and allergenic) but not viable and therefore will not grow and colonize. Mold colonies that do form can be identified down to the species level. This form of analysis takes the longest compared to all options presented here, and fewer testing companies are offering this viable method.

    Water Damage and Survey Process for Mold Inspection

    Healthy Building Science will meet you onsite. We are courteous and considerate of your space and careful not to track in dirt, etc. We are careful not to spread mold spores and cross-contaminate spaces. For mold and moisture inspections we prefer to inspect the whole building, and we take samples only if we believe it will add value for our client. We email or mail our report and follow up with a phone call to answer any outstanding questions.

    In some instances, HBS writes a Mold Remediation Protocol (MRP) outlining requirements for the safe removal of mold from a building. Mold Remediation Protocols are very detailed instructions that include safety requirements and scope of work for your specific project. Our MRPs are designed in accordance with industry-accepted standards (IICRC S520 Mold Remediation Standard).

    Clearance Testing involves sampling before and after remediation. Pre-mitigation samples quantify mold spore counts, identify any particularly virulent species, and creates a baseline for remediation. The post-mitigation “clearance” samples confirm if remediation was performed properly and space was thoroughly cleaned before containment is taken down.

    Bay Area Mold Testing Case Studies

    • Walnut Creek mold testing for multi-family building in a retirement community
    • Santa Rosa mold inspection for school
    • Fremont mold survey for a manufacturing facility
    • San Rafael mold expert for product manufacturing and bottling facility
    • San Francisco mold consultant for high-end custom home
    • Oakland commercial mold testing
    • San Francisco mold inspection for school
    • San Jose mold inspection for data center
    • Berkeley mold survey for a medical office building

    Mold Testing San Francisco Bay Area

    Healthy Building Science is an environmental consulting firm which provides mold inspection services for commercial, residential, multi-family, buildings, offices, industrial and manufacturing workplaces, hospitals and medical facilities, and single-family homes in the greater San Francisco Bay Area and all of Northern California including the cities of San Francisco, San Jose, Oakland, Sacramento, Santa Rosa, Hayward, Sunnyvale, Fremont, Concord, Salinas, Santa Clara, Berkeley, Vallejo, Fairfield, Antioch, Richmond, Daly City, San Rafael, San Mateo, Vacaville, San Leandro, Livermore and Alameda County, Contra Costa County, Marin County, Napa County, San Mateo County, Santa Clara County, Solano County and Sonoma County.

    Call (415) 785-7986 or complete this form to discuss your mold testing needs.



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