Los Angeles mold · Glossary
Mold Glossary: Plain-English Terms from A to Z
This glossary explains the mold testing, remediation, legal and insurance terms used on this site and in Los Angeles inspection reports and quotes. Each definition is short and plain, with a link to the page that covers it in depth. Use it to read a lab report, compare quotes, or talk to your landlord with confidence.
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What do common mold terms mean?
Most mold jargon describes one of four things: how mold is found (testing), how it is removed (remediation), who is responsible (law and agencies), or who pays (insurance). The terms below are grouped alphabetically. If a quote or report uses a word that is not here, ask the company to explain it in writing before you sign anything.
A and B: from ACAC to bulk sample
ACAC. The American Council for Accredited Certification, which issues mold credentials such as CMI (Council-certified Microbial Investigator), CMC (Microbial Consultant) and CMR (Microbial Remediator). California does not license mold inspectors, so private certifications like these are one way to check experience.
AIHA-LAP (EMLAP). The AIHA Laboratory Accreditation Programs. Its Environmental Microbiology Laboratory Accreditation Program (EMLAP) accredits labs that analyze mold samples. Ask which accredited lab your inspector uses.
Air scrubber. A portable machine that pulls air through a HEPA filter to capture spores and dust during remediation. When it is vented outside the work area, it also creates negative air pressure.
ALE (additional living expense). The part of a homeowners or renters policy that pays for a hotel, meals and similar costs when a covered loss makes your home unlivable. Whether it applies to mold depends on what caused the mold.
Antimicrobial. A product applied to cleaned surfaces to slow regrowth. It is a finishing step, not a substitute for removing mold and fixing the moisture source. Spraying alone, sometimes called “spray and pray,” is a common reason mold comes back.
Asbestos. A mineral fiber found in some older popcorn ceilings, flooring, drywall compound and pipe wrap. In older LA homes, suspect materials should be tested before mold work cuts into them. Our mold and asbestos testing page explains when.
Aspergillus, Penicillium, Cladosporium, Alternaria. Common mold groups found indoors and outdoors in Los Angeles. Lab reports list them by name. Their presence alone is normal; what matters is whether indoor levels are higher than, or different from, the outdoor sample.
Black mold. An everyday name usually meaning Stachybotrys chartarum, though many molds look dark. Color does not tell you the species, and the EPA and CDC advise fixing any indoor mold the same way. See Stachybotrys below.
Bulk sample. A small piece of material, such as drywall, carpet or insulation, cut out and sent to a lab to see whether mold is growing in it.
C: from chain of custody to CSLB
Chain of custody. The signed record that tracks a sample from the moment it is taken to the moment the lab analyzes it. It matters when results may be used in a dispute with a landlord, seller or insurer.
Clearance testing. An inspection, usually with air samples, done after remediation and before walls are closed, to confirm the work area is clean and dry. It is best done by someone independent of the removal crew. Read more about post-remediation clearance testing.
Clearance criteria. The pass or fail standard written down before work starts: for example, no visible mold, dry materials, and indoor spore levels similar to the outdoor control.
Condensation. Water that forms when humid air touches a cooler surface, like a window or an outside wall. It causes spread-out mold that is easy to confuse with a leak. Our guide to telling mold from condensation shows the difference.
Containment. Plastic sheeting, tape and zipper doors used to seal off a work area so spores and dust stay inside. The amount of containment grows with the size of the job, from a simple barrier to a fully sealed room with an entry chamber. Our step-by-step remediation process shows what it looks like.
Crawl space. The shallow space under a raised-foundation house. Common in hillside and older LA homes, it can stay damp and grow mold on joists and subfloor. See crawl space mold remediation.
CSLB. The Contractors State License Board. In California, remediation that is part of construction work over $1,000 needs a CSLB-licensed contractor. You can check any license at cslb.ca.gov.
D and E: from dew point to ERMI
Dew point. The temperature at which air has to give up its water as condensation. On humid marine-layer days the dew point is high, so ordinary cool walls and windows get wet.
DOSH. Cal/OSHA’s Division of Occupational Safety and Health. Asbestos work over 100 square feet requires DOSH registration, along with CSLB asbestos certification.
EMC (equilibrium moisture content). The moisture level a material such as wood or drywall settles at in normal indoor conditions. Drying is finished when wet materials are back near that level, which is checked with a moisture meter.
Encapsulant. A coating sprayed or painted onto cleaned wood or framing that cannot be removed. It seals the surface after cleaning. Painting over active mold without cleaning it first is not encapsulation.
EPA 10 square foot guideline. The EPA’s rule of thumb that mold covering less than about 10 square feet, roughly a 3 by 3 foot patch, can usually be cleaned by a homeowner. Larger areas usually call for a professional.
ERMI. The Environmental Relative Moldiness Index, a DNA-based dust test that scores a home against a national reference set of mold species. It was developed by EPA researchers, but the EPA has cautioned that it was built as a research tool. Learn more about ERMI testing in Los Angeles.
H and I: from habitability to IICRC S520
Habitability. A landlord’s legal duty to keep a rental fit to live in, set out in California Civil Code 1941 and 1941.1. Serious mold and the leaks behind it can make a unit fall short. This isn’t legal advice; contact Bet Tzedek or a tenant lawyer about your case.
HEPA. High-efficiency particulate air. A HEPA filter captures at least 99.97 percent of particles 0.3 microns in size, which includes mold spores. It is used in air scrubbers and vacuums during remediation.
HEPA vacuum. A vacuum with a sealed HEPA filter, used to clean dust and spores from surfaces and contents. A household vacuum without one can blow spores back into the room.
HERTSMI-2. A shorter score built from a handful of the species in an ERMI test. Some practitioners who work with mold-sensitive patients use it. It is not an EPA or CDC standard.
Hygrometer. An inexpensive meter that shows relative humidity. The EPA recommends keeping indoor humidity below 60 percent, ideally between 30 and 50 percent.
Hyphae. The thread-like strands mold grows into a material. They are why mold on drywall or carpet often cannot be wiped away and the material has to be removed.
IICRC S520. The ANSI/IICRC S520 Standard for Professional Mold Remediation, the main industry standard for how mold jobs are scoped, contained, cleaned and verified. Its companion, IICRC S500, covers water damage restoration. IICRC certifications include AMRT for mold and WRT for water damage.
L and M: from LAHD to mycotoxins
LAHD. The Los Angeles Housing Department. It handles housing complaints, including mold, inside the City of Los Angeles through its Code and Rent Helpline, (866) 557-7368. Other cities and County areas use different agencies; see who to call about mold in your city.
LA County Public Health, Environmental Health. The County office that takes housing complaints, including mold, in unincorporated areas and in cities that use the County health code, at (888) 700-9995. Long Beach, Pasadena and Vernon run their own health departments.
Lead paint. Paint made before 1978 may contain lead. Disturbing it during mold work falls under the EPA’s RRP (renovation, repair and painting) rule, which requires lead-safe work practices.
Marine layer. Low cloud and fog that drift in from the Pacific, strongest in May and June (May Gray and June Gloom). It keeps coastal homes humid for weeks. Read our June Gloom and coastal mold guide.
Moisture meter. A handheld tool that reads how wet drywall, wood or concrete is. It is the most useful tool in a mold inspection, because it finds the water that mold needs.
Mold. A type of fungus that grows on damp material and spreads by releasing spores. Spores are everywhere outdoors and in every home; mold becomes a problem only when it finds steady moisture indoors. Flat surface growth in showers is often called mildew, and it is treated the same way.
Mold sublimit. A cap in many homeowners policies on how much the insurer will pay for mold, even when the water event that caused it is covered. Check your declarations page.
MVOC. Microbial volatile organic compounds, the gases growing mold gives off. They cause the musty smell that often leads to hidden mold.
Mycotoxins. Chemicals some molds can produce under certain conditions. Their presence and health effects in homes are still being studied. If you are worried about symptoms, talk to your doctor.
N to P: from negative air to PPE
Negative air (negative air pressure). Running a HEPA air scrubber that exhausts out of the contained work area, so air always flows into the containment rather than out of it. In plain terms: a filter fan that keeps spores from drifting into the rest of the home.
Notice to comply. A written order from a code inspector telling a property owner to fix a violation, such as mold or the leak behind it, by a deadline. In the City of Los Angeles, LAHD typically gives owners up to 30 days.
Outdoor control sample. An air sample taken outside at the same time as the indoor samples. The lab compares the two; indoor levels well above outdoor, or different types of mold, suggest an indoor source. Our mold air testing page explains how to read the numbers.
Porous materials. Materials that soak up water, such as drywall, ceiling tiles, insulation and carpet pad. When mold grows into them, they usually have to be removed rather than cleaned.
Post-remediation verification (PRV). Another name for clearance testing: the inspection after remediation that confirms the area meets the agreed clearance criteria.
PPE. Personal protective equipment. For mold work this means at least an N-95 respirator, gloves and eye protection, and for larger jobs a P100 respirator and disposable suits.
R: from relative humidity to RSO
Relative humidity (RH). How much water the air holds compared with the most it could hold at that temperature, shown as a percentage. Readings that stay above 60 percent indoors make mold more likely.
Remediation. The full process of fixing a mold problem: correcting the moisture source, containing the area, removing damaged materials, cleaning, drying and verifying. “Removal” usually means the same thing in everyday use. “Mitigation” often means limiting water damage before mold grows, and “abatement” is a term borrowed from asbestos work. See our mold remediation overview.
Remediation protocol. A written plan, ideally from an independent inspector, that says exactly what areas to contain, what to remove, how to clean, and what clearance criteria must be met. It lets you compare quotes on the same scope. Read about remediation protocol writing.
Repair and deduct. A tenant remedy under California Civil Code 1942 that, in limited cases, lets a renter pay for a repair and deduct it from rent, up to one month’s rent, twice a year. Strict conditions apply, so get legal advice first.
Retaliation. A landlord punishing a tenant, for example with an eviction or rent increase, for reporting a problem. California Civil Code 1942.5 prohibits it.
RSO. The City of Los Angeles Rent Stabilization Ordinance. It covers about 74 percent of rental units in the city, mostly in buildings built before October 1978, many of them older apartments prone to plumbing leaks.
S and T: from SB 655 to Toxic Mold Protection Act
SB 655. A 2015 California law, in effect since 2016, that added visible mold growth to the list of substandard housing conditions in Health & Safety Code 17920.3. Minor mold on surfaces that normally get wet, like a shower, is excluded. Our guide to California mold laws explains what it means for renters and owners.
SCEP. LAHD’s Systematic Code Enforcement Program, which inspects rental buildings in the City of Los Angeles on a regular cycle for habitability problems, including mold and leaks.
Spore. The microscopic particle mold releases to spread. Spores are always present in outdoor air, which is why indoor tests compare against an outdoor sample instead of looking for zero.
Spore trap. An air-sampling cassette that a pump draws a measured amount of air through. Spores stick to a slide inside, and the lab counts and identifies them. It is the most common air test in home inspections.
Stachybotrys chartarum. The mold most people mean by “black mold.” It grows on materials that stay wet for a long time, such as drywall paper after a leak. It deserves to be taken seriously, but it is removed the same way as other mold. See black mold testing.
Structural drying. Using dehumidifiers and air movers to dry framing, subfloors and other building materials after water damage, guided by moisture readings. Drying should be complete before walls are closed.
Sudden and accidental. Insurance language for a water event such as a burst pipe. Mold that follows one is more likely to be covered than mold from long-term seepage, which many policies exclude.
Surface sample (tape lift or swab). A sample taken by pressing clear tape onto a stain or rubbing it with a swab. It tells you whether a spot is mold and which kind, but not how much is in the air.
Thermal imaging. An infrared camera that shows temperature differences on walls and ceilings. Cool spots can point to hidden moisture, which is then confirmed with a moisture meter. The camera does not see mold itself.
Toxic Mold Protection Act. California Health & Safety Code 26100 to 26156. It requires landlords to disclose in writing mold they know about that exceeds limits or poses a health threat (HSC 26147). The state never adopted numeric exposure limits, so there is no official “safe” spore count.
For how these pieces fit together in real homes, read why LA homes get mold or browse more Los Angeles mold guides.
FAQ
Common questions about mold terms
What is the difference between mold remediation and mold removal?
In everyday use they mean the same job. Remediation is the more precise term because it covers the whole process: fixing the moisture source, containing the area, removing damaged materials, cleaning, drying and checking the result.
What does a spore trap test measure?
It measures the types and numbers of mold spores in a set volume of air. The result only means something next to an outdoor control sample taken the same day, because spores are always present outside.
What is clearance testing?
Clearance testing, also called post-remediation verification, is an inspection after mold work that confirms the area is clean and dry before walls are closed. It is best done by someone independent of the crew that did the removal.
What is ERMI testing?
ERMI is a DNA-based dust test that scores a home against a national reference set of mold species. EPA researchers developed it, and the EPA has cautioned that it was built as a research tool, so read the score with someone who knows the building.
What does negative air mean in mold remediation?
It means a HEPA air scrubber exhausts air out of the sealed work area, so air flows into the containment instead of out. That keeps spores and dust from drifting into the rest of the home during removal.
Is black mold the same as Stachybotrys?
Usually that is what people mean, but many molds look black. Only a lab can tell the species, and the EPA and CDC advise removing any indoor mold the same way, whatever its color.
Sources
- EPA, mold guidance, humidity targets and the 10 square foot guideline: epa.gov/mold
- CDC, mold and health: cdc.gov/mold
- ANSI/IICRC S520 (mold remediation) and S500 (water damage restoration)
- Contractors State License Board: cslb.ca.gov
- LA Housing Department: housing.lacity.gov; LA County Public Health: publichealth.lacounty.gov
- California SB 655, Health & Safety Code 17920.3 and 26100 to 26156, Civil Code 1941 to 1942.5
Last updated November 2026.
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