Small amounts of  liquid or a solid particle, which can remain suspended in air for some time.


A substance (such as a mold spore) that can elicit an excessive immune response (allergic reaction) such as hay fever, rashes, sinusitis, or asthma symptoms.


An item (material, substrate, etc.) that supports the active growth and proliferation (increase in numbers) of mold.


An agent used to suppress or retard microorganisms on direct contact (e.g., a fungistatic agent is used against fungi).


Aspergillus is a genus consisting of several hundred mold species found in various climates worldwide. It is highly aerobic and found in almost all oxygen rich environments.  Aspergillus species are common contaminants of starchy foods (such as bread and potatoes), and grow in or on many plants and trees.


Airborne particles or matter of biological origin (derived from a live or formerly living organism). For example, mold spores or fragments of a mold growth that are suspended in the air.


Biocides and fungicides are chemicals that limit the growth of or kill microorganisms such as fungi.

“Black mold”

The poorly defined term “black mold” or “toxic black mold” has usually been associated with the mold Stachybotrys chartarum. While there are only a few molds that are truly black, there are many that can appear black. Not all mold that appears to be black is Stachybotrys.


Fungi are neither animals nor plants and are classified in a kingdom of their own – the Kingdom of Fungi. Fungi include a very large group of organisms, including molds, yeasts and mushrooms. There are >100,000 accepted fungal species but current estimates range to 1.5 million species.

Hidden mold

This refers to visible mold growth on building structures that is not easily seen. This can include inside walls (between the drywall and exterior wall), under the floors (subfloor), in the ceiling and attic space or within the ducting of a heating/ventilation system.

Microbial Volatile Organic Compounds (MVOCs)

Fungi (mold) produce chemicals as a result of their metabolism. Some of these chemicals (MVOC’s) are released as gases in the air and are responsible for the characteristic moldy, musty, or earthy smell.


Molds are a group of organisms that belong to the Kingdom of Fungi (see Fungi). Even though the terms mold and fungi had been commonly referred to interchangeably, all molds are fungi, but not all fungi are molds.


Mycotoxins are compounds produced by some fungi (ie. mold) that are toxic to humans or animals.


In order to reproduce, molds produce spores, which spread through air, water, or by insects. These spores act like seeds and can form new mold growth if the conditions are right.


Stachybotrys chartarum is commonly associated with black mold. It is sometimes found in soil and grain, but mostly found on cellulose-rich building materials in damp or water-damaged buildings (ie. wood, paper, drywall).

“Toxic Mold”

The term “toxic mold” has no scientific meaning since the mold itself is not toxic. The metabolic by-products of some molds may be toxic (see mycotoxin).

Mold Remediation/Standards Definitions

Condition 1 Environment

A condition 1 environment is a term used to describe “normal” air quality levels (this is relative to the location of the environment).

Level 1 Contamination

Small Isolated Areas ( 10 sq ft (0.93 m2) or less) for example, ceiling tiles, small areas on walls.

Level 2 Contamination

Mid-sized Isolated Areas (10-30 sq ft) – for example, individual wallboard panels.

Level 3 Contamination

Large Isolated Areas (30-100 sq ft) – e.g., several wallboard panels.

Level 4 Contamination

Extensive contamination (greater than 100 contiguous sq. ft in an area).

Level 5 Contamination

Extensive contamination (level 4), including HVAC systems (heating, ventilation, air conditioning).