Converting an ISO Class 8 Cleanroom to ISO 7

[TheBigChill]

Hi there,

I'm not quite sure that this is the best place to ask this but, as a recently appointed "Cleanroom Coordinator", I've been tasked with implementing an ISO 7 clean-space within our existing ISO 8 cleanroom.

Our customer is requesting that their product be built in an ISO 7 clean-space, and I'm currently weighing different options regarding how I can implement this. Below are my options, ordered from most to least preferred.

Options:

1) Re-work existing ISO 8 cleanroom to ISO 7 level. (What's involved?)
2) Install modular IS0 7 softwall cleanroom in existing ISO 8 area (encompassing project specific tooling and workspace).
3) Install vertical laminar flowhoods over the project specifictooling and workspaces.

In terms of particle counts, we actually monitor data daily, and with the exception of 5 micron particles we are well within ISO 7 limits. Should I be looking more at better gowning and operator contamination controls, or a better cleaning protocol? Basically, that 5 micron count is all that's keeping us from being ISO 7.

We currently don:

-Bouffant caps.
-Beard covers.
-Washable ESD frocks.
-Disposable ESD cleanroom gloves.

HEPA Coverage:
-5 HEPAS providing ~10% ceiling coverage.

Air changes will be calculated shorty, but I'm fairly certain even those already meet ISO 7, or can with some tweaking of fan speeds and air handler damper adjustments.


Perhaps making shoe covers and sleeve guards (we have a cuff exposure issue) mandatory, that will help.

Thoughts?

 

[MIREGMGR]

Re: Converting an ISO 8 Cleanroom to ISO 7

What does your count data tell you about sources of particles? I.e., if the room has less of a 5 micron issue with systems running but no persons working; or less of an issue with persons working but not circulating; or with some kinds of work-activity/products compared to others; or in parts of the room where particular activity occurs or a particular source may be concentrated. That should point toward what to change first if you choose to bring the whole room to 7.

Is the cheapest solution the one that will be chosen? If so, I assume that the cheaper of the modular and hoods ideas would determine the cost threshold for whole room modifications. Does it seem plausible that the cost of whole room upgrades could fit within that budget?

 

[BradM]

Re: Converting an ISO 8 Cleanroom to ISO 7

Miregmgr points are sound. Basically you need to determine what the cleanroom (irrespective of people and activities) is capable of reproducing.

I've seen situations where clean suites are constructed to meet requirements two grades better than what they were currently classified at. I've also seen situations where the suites were barely passing their current desired specification.

I assume the HEPA filters are testing for downstream velocity and are acceptable. Also, I assume that differential pressures are acceptable.

So, if the room (at rest) can meet the specifications, then to your point, you will need to minimize the burden carried in/out of the room.

 

[TheBigChill]

Re: Converting an ISO 8 Cleanroom to ISO 7

What does your count data tell you about sources of particles? I.e., if the room has less of a 5 micron issue with systems running but no persons working; or less of an issue with persons working but not circulating; or with some kinds of work-activity/products compared to others; or in parts of the room where particular activity occurs or a particular source may be concentrated. That should point toward what to change first if you choose to bring the whole room to 7.

Is the cheapest solution the one that will be chosen? If so, I assume that the cheaper of the modular and hoods ideas would determine the cost threshold for whole room modifications. Does it seem plausible that the cost of whole room upgrades could fit within that budget?

Because particle counts for all sizes are within ISO 7 spec with the room "At Rest", that tells me that our biggest contamination burden is likely personnel. Shortly after a couple of people walk in the room ("In Use"), the 5 micron particle count goes outside ISO 7 spec, while all others stay in. Having said that, it's a bit perplexing as to why this happens, as we don all suggested and required apparel. Perhaps we need to look at upping our cleaning standards?

In terms of processes within the cleanroom that contribute to contamination, we use primarily hand tools and electronics test equipment, with three, slow rotating fixtures. I'd consider them pretty low contributors to contamination. Occasionally soldering takes place, and even with a elephant trunk sucking the smoke away, sometimes our particle counter goes nuts.

The cheapest option won't necessarily be the chosen option, but we do have an unused modular softwall cleanroom, and 4 HEPAs / FFUs that are currently unused and could be applied to the project. The issue with the modular softwall room is ceiling height; Our ISO 8 cleanroom has an 8' ceiling, and the top of the HEPAs for the softwall room are also around 8'. You must have 1' of clearance between HEPA ceiling outlets and HEPA inlets of hoods or modular cleanrooms.

Some Technical Data:

- 5% of our ceiling is HEPA filters (I misspoke earlier).
- We have 28 Air Changes / Hour.
- 60% Humidity and 69F temp.
- Room pressure differential is .08.

In order to convert to ISO 7, we'd have to add ~ 10 more HEPAs to achieve 16% ceiling coverage, and fine-tune the fan speeds on all units in order to achieve 40-60 Air Changes / Hour. (Based on Flanders Air cleanroom design guidelines.)


One thing I'm currently handling is our personnel and their bad habits of bringing paper, ESD cardboard, and other non-cleanroom approved material into the room. Additonally, we don't have a gowning room. People use the tacky mat outside the door, and gown-up in a corner near the entry door. This is also changing, as we're building a gowning room.

Thanks for the responses, guys, and any help is appreciated.

 

[BradM]

Re: Converting an ISO 8 Cleanroom to ISO 7

I wished all posters provided details like this.

Because particle counts for all sizes are within ISO 7 spec with the room "At Rest", that tells me that our biggest contamination burden is likely personnel. Shortly after a couple of people walk in the room ("In Use"), the 5 micron particle count goes outside ISO 7 spec, while all others stay in. Having said that, it's a bit perplexing as to why this happens, as we don all suggested and required apparel. Perhaps we need to look at upping our cleaning standards?

I couldn't imagine the 5 micron shooting up, and not the .5 micron. I agree with your statement about cleaning. Something (or somebody) is bringing in some nasty stuff.

Have you measured with increased gowning requirements in place?

In terms of processes within the cleanroom that contribute to contamination, we use primarily hand tools and electronics test equipment, with three, slow rotating fixtures. I'd consider them pretty low contributors to contamination. Occasionally soldering takes place, and even with a elephant trunk sucking the smoke away, sometimes our particle counter goes nuts.

Do you perform this work in flow hoods?

The cheapest option won't necessarily be the chosen option, but we do have an unused modular softwall cleanroom, and 4 HEPAs / FFUs that are currently unused and could be applied to the project. The issue with the modular softwall room is ceiling height; Our ISO 8 cleanroom has an 8' ceiling, and the top of the HEPAs for the softwall room are also around 8'. You must have 1' of clearance between HEPA ceiling outlets and HEPA inlets of hoods or modular cleanrooms.

It's nice to have options.

Some Technical Data:

- 5% of our ceiling is HEPA filters (I misspoke earlier).
- We have 28 Air Changes / Hour.
- 60% Humidity and 69F temp.
- Room pressure differential is .08.

Is that room differential to.. open (unclean air) that seems kind of low. I would like to see that up higher if possible. Now... if you were talking a cascade scenario and this was three tiers up, .08 may be all you can get. Are they going in and out of the door a lot? Is there a gown room leading in?

One thing I'm currently handling is our personnel and their bad habits of bringing paper, ESD cardboard, and other non-cleanroom approved material into the room. Additonally, we don't have a gowning room. People use the tacky mat outside the door, and gown-up in a corner near the entry door. This is also changing, as we're building a gowning room.

Um... maybe if I actually read everything, I could see your answers to my questions!

Personally, I think having a gown room will make a big difference. Since you already have this under Change Control and such, can you up the air flow in the clean room, up the air flow in the gown room, and then have cascading positive differentials? I think that would help a lot.