In Reply to Parent Post by SGquality
I would like all experts to comment on the engineering aspects of the Clean Room and not considering the product.
Conceptually, would a clean room be designated entirely based on particle counts ? If it was a Class 5 clean room, there are lots of things required like gowning / degowning area, wearing sterile garments etc. Like these, would there be any additional requirements between Class 7 and 8 ?
Sorry for taking this long
A class 7 clean room is 10 fold better than class 8 as you can see from the ISO14644-1.
So the gowning, materials selection and cleanroom behaviour must be more better to always maintain a class 7 as compared to class 8.
Some details below for particle details.
Where do particles come from?
Clean Room Air
The task of the Clean Room filter is to ventilate the atmosphere with microbial and particulate free air. They create a positive pressure, so that any air-borne contaminants present are from within the room.
The source of micro-organisms is from people.
The source of particulates are from people and processes.
Microbes are dispersed from skin cells, and a human body sheds the outermost layer of skin every 24 hours.
1 BILLION SKIN FLAKES EVERY 24 HOURS.
A skin flake is typically 33 microns - 44 microns. They break down to typically 20µ (micron) but 7-10% are less than 10µ (micron). The equivalent diameter of bacteria carrying particles is 12-14µ (micron). These settle by gravity at 0.37 meters per second.
12-14µ (micron) size particles will settle in wounds of hospital patients and aseptically filled containers in pharmaceutical applications by gravity.
Particles from people are dispersed:
From their skin
From their normal outdoor clothing
From their Clean Room clothing (both through it and from the surface).
The mixture of skin flakes and fabric fibers fragment into smaller pieces, so that the total number of particles is:
10 BILLION EVERY 24 HOURS. This figure is dependent on activity rate, work activity, more particles.
Demonstrations have indicated that typically this means:
1 MILLION PARTICLES EQUAL TO OR GREATER THAN 0.5 MICRONS ARE DISPERSED EVERY MINUTE.
They disperse into the air from exposed skin, through the apparel fabric and also out through the neck, waist, trouser opening and wrists.