Unkown white powder found in duct downstream of HEPA! 1

[zhangbd]

Hello,
We're experiencing a serious non-conformance events that inspector has found out some unkown powder were blowing out of room vents, which dropped on the floor like floc, and it could be pressed and grinded into white powder by your fingers.
Air is humidified and filtered(H14) after output, several days before we ever increased the air press to meet
the requirements of rooms air flow criteria.

We're wondering what the powder is. and where it from?

Who could help me on this? Looking forward to.....

Borjn Zh

 

[quark]

Is your system once through or recirculatory? Where are you finding this powder, in the exhaust or in the controlled space? What are you manufacturing? What is the position of room return(floor level or ceiling level)? Are the filters integrity tested? What is the function in areas adjacent to this controlled room?

Regards,

 

[zhangbd]

Dear quark,

Thanks for your concern, That HVAC is once through system, we are finding this powder on the floor,and also on the material bags, seems everywhere in the controlled area. The return points are at the floor level, and we conduct integrity test annually by third-party service. We are a pharmaceutical plant and this controlled room is weighing area, supplied by this hvac separately.

Now we're doubt whether this unknown powder coms from HEPA? Maybe high face velocity ruptured the fiberglass, we're checking the HEPA....

Thanks for your further guides

 

[quark]

All dispensing areas should be negative w.r.to the adjacent areas and I presume you meet this requirement. Further, you should carryout dispensing in a reverse down flow laminar booth. The powder may either be excipient or active ingredient.

This is not a problem with HEPA filters.

Check your return risers for presence of this powder. If you find traces then the velocity in the return may not be sufficient.

Next time, try the dispensing activity in a closed booth and check for the presence of this powder outside.

Regards,

 

[tbrght]

Have you tried using demineralized water in your humidification system? I had this problem several years ago as a maintenance manager at a university. We had very hard water on campus. We used water softeners on our water system but had to go to distilled water to eliminate the fine white powder.

 

[zhangbd]

Thanks very much, quark and tbrght:

We have tried out every repair to indentify root cause: clean out the duct, change all of HEPA, and even check& clean all damps on duct, but the unkown white powder still blow out continually.

is it zinc oxide? i think the high humudity air throgh the long galvanized duct may increase its oxidating speed.

regards

 

[SAK9]

Why not send it to the lab and get it analysed? Once you know what the material is,the investigation will be easier

 

[ChasBean1]

zhangbd,

I've seen a similar problem in a pharmaceutical building. The problem was bad air handling unit design. Here was what happened:

The outside air intake on the 100% OA system was of fairly high velocity and occasionally took in snow and rain. The filter media frequently became wetted, and released some of the liquid onto the heating coil just downstream.

Due to the make-up of the filters, droplets of water from these wetted filters contained high levels of chloride, sulfate, and phosphate. The heating coil, wetted with this solution, rapidly evaporated the water, forming concentrated pockets of corrosives on the aluminum coil fins.

Accelerated coil corrosion results in formation of aluminum oxide chips, which look like particles of dandruff when they fall onto surfaces.

My guess is that some phenomena, either a situation as I just described, or an improperly controlling humidifier corroding a heating coil, is creating the condition you describe.

 

[zhangbd]

Very thanks to everyone for your concern,

Colleagues from lab said this unkown white powder is aluminum oxide, so till to now, we can make a conclusion to this case, even though which has brought us so much trouble.

It's caused by bad AHU designed, like ChasBean1 described above, the air downstream the humidifier with high velocity and nearly 90% humidity occasionally has corrosive action to the aluminum galvanized duct, on the surface, points there are rivets and cutted holes for valves installation always are weakly to anti-corrosion, so results in aluminum oxide formed on and be blown down to controlled area, looks like particles of dandruff.

Too long duct installed downtream the humidifier causes to form this white aluminum oxide. We have inquired about this case to some consultant firms for betterments, they suggested we should modify existing AHU layout and put the HEPA at the vents in accordance with the cGMP.

I also think this problem is normally to each HVAC, so I want draw everyone full attention on this case.

 

[SAK9]

In my earlier days, we used to fabricate clean room ducts using aluminium(usually one gauge higher than recommended by the stds such as SMACNA for better strength).That does not seem to be case now.

I beleive that they use zinc for galvanization of metal sheets.So it could be the AHU coil aluminium fins giving away as suggested by CB.