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Old 09-04-2019, 12:45 PM   #2837
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Join Date: Jun 2001
Posts: 56,176
Stachybotrys mold which is common in the FCU is really the worst as the symptoms are often severe. Mold often go undetected simply because customers cannot see it hidden deep in the unit and coil even if they go looking for it and even if it spreads to the visible parts it is often mistaken it for dust. The only easy way to detect mod is via the characteristic weird musty smell during turn on, but that already signifies that the mold infestation is quite serious.

While ozone, superheated steam, 185 or 254nm UV-C, chemicals like biocides, fungicides, benzalkonium chloride and other methods can kill mold and prevent it from reproducing, the dead mold spores can still effect health and trigger allergies as the allergenic substances are found on the outer shell, so it has to be physically removed and flushed away. What happens in a severe infestation is that layers accumulate and really takes pressure washing as a physical means to effectively remove it. If you are referring to allergy cases, it takes total removal to be considered a successful project. A very minute amount of it aerosolized can still trigger symptoms.

Anything less than 99% removal rate is considered to be mediocre in the effect of the end-user even in a small scale case in the home FCU simply because the air in the enclosed room is greatly recycled and so the levels build up gradually but consistently. Re-infestation also occurs rapidly in a humid environment of more than 60% humidity if there are nearby sources of mold spreading spores that are left untreated, unless if you can do cleaning very regularly with a maintenance routine of no longer than 4 weeks between cleanings. Of course this means good business for us.

We only hit it with the 10 bar 150 PSI high pressure dry steam cleaner and also with 20 bar 300 PSI compressed air in commercial settings that require it, especially in sensitive FnB and clinical settings with wall-mounted and cassettes where we would also pull in a 10 inch compressible exhuast duct with axial fan and exhaust it to the external environment just to be safe and cover our asses to put it crudely. Typically with AHUs, we hit it fast and hard with chemicals and the power washer which do the job more effectively and efficiently, unless the customer specifically requests for the dry steamer to be deployed.

N Thailand has been experiencing heavy haze and i have also been posting in their thaivisa forum haze threads and air purifiers/HEPA filtration, 3M filtrete and various electrostatic methods etc........ had the opportunity to correspond with a "farang" (ang moh) cleaning professional who owns a company that does cleaning jobs in Chiang Mai city area. He sounds to be quite high-end type.

It sounds like steam cleaning even at high pressure is still unable to totally remove mold, even though it might clean and disinfect the coil and blower and maybe even the back/internal sides of the FCU. Dead mold spores still presents a problem if not removed.
1-hr ug/m3 + PSI
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