movement through an HVAC system may furnish ample food for mold. Since the air-conditioning system is not always running, warm conditions are the final component for mold growth. Assessment An observation of the indoor environment should be conducted before any sampling is performed. The area should be surveyed for odors indicating mold or bacterial growth, moisture sources, such as stagnant water or leaking pipes, and water-damaged building materials. This can include moving furniture, lifting (or removing) carpets, checking behind wallpaper or paneling, checking ventilation ductwork and exposing wall cavities. Efforts typically focus on areas where there are signs of liquid moisture or water vapor (humidity), or where moisture problems are suspected. Often, quick decisions about the immediate safety and health of the environment can be made by these observations before sampling is even needed. The United States Environmental Protection Agency (EPA) does not generally recommend sampling unless an occupant of the space has symptoms. In most cases, if visible mold growth is present, sampling is unnecessary. Sampling should be performed by a trained professional with specific experience in mold-sampling protocols, sampling methods and the interpretation of findings. It should be done only to make a particular determination, such as airborne spore concentration or identifying a particular species. Sampling Before sampling, a subsequent course of action should be determined. In the U.S., sampling and analysis should follow the recommendations of the Occupational Safety and Health Administration (OSHA), National Institute for Occupational Safety and Health (NIOSH), the EPA and the American Industrial Hygiene Association (AIHA). Types of samples include air, surface, bulk, dust, and swab. Multiple types of sampling are recommended by the AIHA, since each has limitations. Air sampling Air is the most common form of sampling to assess mold levels. Although, the Environmental Protection Agency (EPA) does not have any current testing protocols. Air sampling is considered to be the most representative method for assessing respiratory exposure to mold. Indoor and outdoor air are sampled, and their mold spore concentrations are compared. Indoor mold concentrations should be less than or equal to outdoor concentrations with similar distributions of species. A predominant difference in species or higher indoor concentrations can indicate poor indoor air quality and a possible health hazard. Air sampling can be used to identify hidden mold and is often used to assess the effectiveness of control measures after remediation. An indoor mold air sampling campaign should be performed