Mould remediation guidelines – Part 1- New York City Guidelines

Guidelines on Assessment and Remediation  of  Fungi in Indoor Environments New York City Department of  Health and Mental Hygiene (November 2008)

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NEW YORK city has developed formal mould remediation guidelines in 1993 and since then these guidelines have been subjected to several revisions namely in 2000 and in 2008. The principal aspect of the guideline document is the recognition of the visual inspection involving the categorization of the extent (square meters) of mould growth on interior surfaces as the most important component of the assessment process. Air sampling for specific mould contaminants is not viewed as an essential component of the assessment process.


Remediation strategies according to the 2008 document are based primarily on the amount of mould found during the inspection process. Two situations are considered in the document e.i. the removal of mould from the interior surface finishes and removal of mould from HVAC systems. Specific aspects of each removal process are based primarily on the extent of the mould contaminated area.  NYC guidelines recognise three levels of contamination for interior areas, SMALL (less than 1 m2), MEDIUM (1-10m2) and LARGE (more than 10m2) and two levels of mould contamination in HVAC systems; SMALL (less than 1 m2) and LARGE (more than 1 m2).

The need for suitable personal protective equipment is clearly defined in the document. It states that mould remediation operatives are likely to be exposed to levels of microbial matters (spores, hyphae, fragment etc.) at levels sufficient to be associated with onset of organic dust toxicity syndrome (ODTS) and hypersensitivity pneumonitis (HP).

Limited advices given in the document on cleaning techniques applicable to porous and non- porous materials. It states that non-porous materials (hard plastics, glass, metals) can be sufficiently cleaned. Semi- porous and porous materials, such as concrete and timber can be sufficiently cleaned if they are structurally sound. It is however recommended to remove and discard all porous materials (such as insulation, ceiling times, carpets, cloth etc.)


The use of antifungal and biocidal agents (chlorine dioxide, ozone and other chemical treatment agents) is not recommended and should not be used as a substitute for proper and thorough mould removal. Special precautious must be taken if chemical treatment agents are applied to HVAC systems. The document states that chemical agents must be specifically approved and certified to be used in HVAC systems. In cases where materials are likely to be exposed to elevated moisture the use of biocidal agents might be necessary.


The level to which the affected area needs to be isolated depends on several factors but mainly on the extent of the mould contamination, degree of disturbance associated with the removal operations and proximity of occupants.


Independent and impartial quality control is an essential part of any mould remediation project. The document recommends in order to ensure the effectiveness of remediation check the following indicators:

Root cause of the contamination was identified and resolved;

  • Isolation of the work area was appropriate and effective;
  • Mould removal was carried out in accordance with pre-approved work specific plan;
  • Upon completion of remediation, surfaces are free from visible dust and debris.
  • If environmental sampling was performed, the results of such sampling were evaluated by a trained building or environmental health professional.

By Tomas Gabor

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