Chapter 4 – Cleaning and restoration procedures
All cleaning and restoration procedures must achieve, as a minimum, a “visibly clean” condition, or any specific cleanliness level defined in the contract.
[…] All equipment used to create negative pressure in the ducts that is not equipped with HEPA filtration must exhaust to the outside of the building.
Access openings in the ductwork must be installed in such a way that they do not compromise the structural, thermal or functional integrity of the HVAC system. They must not restrict or alter the airflow inside the ducts. The materials used must comply with applicable safety standards and national technical regulations.
[…] Where access panels are made of fibreglass, the fibrous material must not be in direct contact with the internal airstream.
[…] The HVAC system must be cleaned using appropriate mechanical cleaning devices combined with vacuum collection to capture the dislodged contaminants.
If “wet” cleaning (water, steam, detergents) is used, the cleaning solution must not damage system components and must not be directed onto electrical components, fibreglass materials or other porous components.
[…] It is recommended that “wet” cleaning also be carried out on air-handling components (fans, coils, condensate pans, non-porous surfaces, etc.). Wastewater must be properly collected and disposed of.
[…] Air ducts must be cleaned in such a way as to remove all non-adhered substances and to pass the NADCA verification tests.
[…] Cleaning operations must not alter or damage any smoke and fire detection devices located within the HVAC system.
[…] To demonstrate the effectiveness of coil cleaning, it is recommended that static pressure measurements be taken before and after cleaning.
[…] Surfaces and components of the HVAC system that have suffered water damage must be inspected, cleaned and, where necessary, repaired or replaced. The same applies to components damaged by fire, heat or smoke.
Chapter 5 – Verification of cleanliness and documentation
All components subjected to cleaning must undergo the following tests to verify compliance with this standard.
Verification must be performed immediately after the cleaning operations and before the system is returned to service.
Method 1 – Visual inspection
This must be performed for all porous and non-porous surfaces. A surface is considered visibly clean when no dirt or non-adherent substances are present.
If visual inspection does not give a clear result, the following test is recommended.
Method 2 – Surface comparison
This method applies to both porous and non-porous surfaces. Surface conditions are evaluated by visual comparison before and after the following operation: the test surface is cleaned by passing a vacuum brush over it four times; the drawn air is filtered through a HEPA filter until the collected dust causes a predefined increase in pressure drop across the filter. At this point, a visual inspection of the surface is carried out and the operation is repeated until no significant visible changes are observed.
If the comparison method does not give a clear result, the following test may be performed.
Method 3 – NADCA Vacuum Test
This method applies only to non-porous surfaces.
A template with two slots measuring 2 cm x 25 cm is applied to the surface to be tested. A cassette dust filter (containing two cellulose ester membranes – MCE – in series, 37 mm in diameter, 0.8 micron pore size) is connected to a vacuum pump (set at 15 L/min ± 5%) and passed over the slots in the template. The cassette filter never touches the test surface, but the particular configuration of the template promotes migration of dust particles from the surface to the filter under the action of the vacuum.
Dust loading is measured by gravimetric analysis of the filters, and the result is expressed in mg/100 cm².
For the surface to be considered “clean” according to the NADCA Vacuum Test, the amount of dust collected must not exceed 0.75 mg/100 cm².