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Featured Mold – Aspergillus and Penicillium

Aspergillus and Penicillium are two of the most common mold genera that we see in air samples.  When dealing with spore trap lab results, you will often see these types listed together in groups such as Aspergillus/Penicillium, Asp/Pen, or Pen/Asp. Visually, spores of these genera are so similar that analysts can not differentiate them, so they are reported together. Occasionally spores from other genera that produce similar small amerospores (spores with no septations and no projections longer than the length of the spore) will be counted in this group also. Because there are over 200 separate species of both Aspergillus and Penicillium, an Asp/Pen designation on a lab report represents a large grouping of different species.

microscopic photo of aspergillus
Aspergillus conidia at 400x

Since there are so many different species in this group, we can find Aspergillus and Penicillium in a broad range of habitats. Some species such as Aspergillus penicillioides are xerophilic, which means they grow with only a small amount of moisture. Other species like Aspergillus versicolor are more prevalent in environments with high water activity. In a home without any moisture problems you can often find Aspergillus and Penicillium growing on spoiled fruit.

Like all mold, Asp/Pen can cause allergic reactions in people who are sensitive to these types. They can also occasionally cause fungal infections of the ear, eyes, and skin.  In people with underlying health issues and compromised immune systems, Aspergillus can infect the lungs causing pulmonary aspergillosis.

Surprisingly, mold isn’t always the bad guy. There are many important uses for fungi in industry. For example, Aspergillus and Penicillium are used to make all sorts of products from cheese to pharmaceuticals. Without these fungi we would be without many important antibiotics, soy sauce, or soft drinks.

Ian Cull

Ian Cull is a nationally recognized expert in the field of indoor air quality. He is the Chief Science Officer of Indoor Science, a company he started in 2004. He speaks around the world on air quality topics and is a training provider of the Indoor Air Quality Association. Mr. Cull is a Licensed Professional Engineer (PE) and Certified Industrial Hygienist (CIH). His degree is in Environmental Engineering from the University of Illinois - Urbana Champaign. Mr. Cull has developed 50 air quality related courses for the IAQA University and is the author of the book, “Fundamentals of Mold Remediation”. In his words… “Besides being passionate about indoor air quality, I enjoy cycling, music, the Chicago Bulls, and having fun with my three kids.”

23 thoughts on “Featured Mold – Aspergillus and Penicillium

    Dylan hi there. I had an air sample dine in bedroom and was told it was aspergilus penicillium and the reading was 13,000. I’m supposed to get an official report tomorrow along with remediation plans. Do you think this data would it explain some health issues. And is it worth moving away for some time or getting a second opinion. Plate test and ERMI didn’t show these molds. Thank you.


    It is possible that people sensitive to these types of mold may experience symptoms to this exposure. 13,000 spores/m3 would be considered an elevated amount in a typical air sample. Plate tests and ERMI tests can miss a lot of issues, which is why we always suggest doing air sampling in coordination with ERMI testing.

    Hi, We have floors buckling in our double wide, after investigating we found we had mold on our floors. We had some plumbing work done a few months ago and come to find out, they left the belly wrap down and we live in Fl. Moisture and heat traveled between the belly wrap and the floor causing mold growth. We have Asperaillus/Penicllium at high levels and scopulariopsis/microascus at medium levels in approx. one half of the house. Both of use have heart conditions and COPD, how concerned should we be to continue living in our home, and can we remove the floors ourselves or do we have to hire a company to do the removal?


    The EPA suggests that any mold problem over 10 sf in area be addressed by a professional. Since people’s reaction to mold is do different person to person, there are no established “safe” or “healthy” levels for mold. As an environmental professional, I can’t make that determination.

    Hi I’m currently having my apartment redone because air conditioning,was going bad released water behind the wall and went on carpet they left it therefor a month but the first time it was a year and left on floor I did the samples and took to labAspergillosis penicillium I have 3autoimmune disorders since there was the damage a year ago I’ve had pneumonia with sepsis 3 times and since they never cleaned the mold safely every time I go there I’m sick with throat and breathing problems

    The crawl space under our house has been diagnosed as containing ASP-Pen, according to the tech the elevation is quite high. We need to clean out about 10 yards of junk ,I am wondering what the exposure might cause while removing it.

    Hi there,
    So are aspergillus and penicillin related, or do they just bear resemblance to each other? Trying to understand this from a possible allergy standpoint. If someone is allergic to one, what is the likelihood of them being allergic to the other?

    They are grouped together on air sampling reports because visually, the spores are almost impossible to reliably differentiate. Taxonomically they are as related to each other as humans are to gorillas. Allergies are very individualized, some people are allergic to both, others are allergic to just one, and some are only allergic to specific species. The only way to know would be to have a detailed mold allergen test done by a doctor.

    I have 300m3 of asp/pen in my rental unit. Is that dangerous? I being sued by my tenant for this.

    Recently had an a/c unit (not central air) with a clogged condensate line causing water to accumulate within the unit. Not certain how long this went unnoticed but was likely a matter of 4 to 6 months. The unit has been removed and replaced. Air quality testing shows aspergillius/penicillium. Does This this require full remediation . I do seem to have an allergy related to this.

    Count per m/3 – 121 – 25%

    Aspergillus and Penicillium are made up of hundreds of different species, each with their own specific preferred growth conditions. I do not know of any specific species that can grow on almonds, but I can only assume it is possible.

    So I have Aspergillius and Pennicilium in me according to a urging test. Should I stop eating all cheese if I am allergic to the spores?

    What is your favorite method of remediation for Penicillium/Aspergillus in the wall cavity of a home?
    I’m desperately seeking truth as I have autoimmune disorders and can’t be exposed to the mold. Yet, we’d have to sell our home after the costs of traditional remediation.
    We are being directed by our inspector to local company that uses a dry fogging product called InstaPURE (a Sterilant) then followed EverPURE. It’s the second dry fog application in the two-step process that supposedly prevents the mold from returning. The company markets it as the only fogging BioStat of its kind to be approved by the EPA for mold remediation.
    Any information you can share would be deeply appreciated.


    Fogging is not a proper way to remediate any types of mold. The goal for remediation is the physical removal of mold from the building materials. Fogging may kill mold, but it does not magically make it disappear. Even dead mold can cause allergic reactions in susceptible people, so the mold needs to be physically removed from the space.

    I just had air tested in condo and it was positive for Aspergillis/penicillin like mold at 8,800 count.
    There are dome black spots on popcorn ceiling in one area…not much.
    Should I be concerned?
    Am I In danger?

    We are not medical professionals so we are not qualified to say if your health is at risk.

    With the info you have provided there is not much I can say, it is the industry standard to compare air samples to an outdoor air sample taken at the same time.

    Can you comment on an air test that does have outdoor vs indoor spore count? Trying to get information on levels.

    We are in a rental, have lived here for 5 years. During this time multiple water leaks from roof issues, internal plumbing from upstairs bathroom down walls in 1st floor entry way which required repair. Never convinced repairs got everything, had a test done and came back with the following elevated levels:

    Control Front: 5/200/3.1%
    Control Back: 2/80/1.1%
    Master Bedroom: 18/760/35.5%
    2nd Bedroom: 30/1300/37.9%
    Living Room: 32/1400/32.6%

    Control Front: 23/970/15%
    Control Back: 16/680/9.1%
    Master Bedroom: 16/680/31.8%
    2nd Bedroom: 10/420/12.2%
    Living Room: 36/1500/34.9%

    Control Front: none
    Control Back: none
    Master Bedroom: 1/40/0.9%
    2nd Bedroom: none
    Living Room: none

    Immediate Question: Are the levels of Asp/Pen safe to be in the home?