This article is meant to de-bunk some of the commonly used sales techniques in order to further certain manufacturers agendas to the detriment of customers.

The following are facts – not fiction.

Comment
1. Static attraction on plastics will cause a large cleaning problem.
Fact – Static attraction on materials like polycarbonates which are far out on the triboelectric charge chart is based on two factors – 1.) Surface rubbing with de-similar material – ie. wiping down room with dry poly wipe and/or 2.) Humidity present in the room. Any humidity levels below 30% RH can contribute to an overall static electricity build up in the room. This would include conductors (metal) not grounded as well as all non-conductors (plastics) in the room. Plexiglas panels in a normal bay area environment will not hold large charges for long periods of time. This is a non-problem. When cleaned as part of a routine maintenance program we recommend using a Tech spray (Amarillo, Texas) antistatic cleaner which topically coats the plexi with cleanroom approved – minimum out-gassing, non-tiertiory amino-acid material. This cleaning performed once per month is a good start for a maintenance program. The fact is – a softwall room presents a much larger cleaning problem as a flexible material is much harder to clean properly than a rigid material. Also the mounting mechanism of a softwall room is not as air tight and tends to collect debris and contaminants which are very difficult to remove.

A smooth, tight fitting, easily cleaned surface is always best for a cleanroom wall. Also plexiglas does not scratch unless you clean it with sand paper. We have pristeen facilities that have been installed for over 10 years without unsightly scratches. Just be careful.

Comment
2. ESD is a concern –
Fact – ESD refers to electrostatic discharge. This is an event much like receiving a shock from a door knob. Huge charges are necessary for this event to occur and be felt between a human and a facility wall. This concern relates, in most industries, to component level and some board level electronics.

This would occur when a transfer of static charge alters the reliability (walking wounded) or outright destroy a component. (IC) This can occur in less than 5 volts. However most industries do not have this problem and referring to ESD instead of static attraction of particulates (comment #1) just indicates technical ignorance.

Comment
3. Flex wall curtains do not outgas.
Fact – All plastics outgases due to the fact that they need a binder to hold them together. Many softwall cleanroom manufactures are hard-put to produce valid documentation as to the true cleanliness of their product or their flame spread ratings for uniform building code purposes. The thing you smell when you open the box with new plastic – that’s out-gassing. Please think about it.

Comment
4. If it’s a temporary installation or a “tent cleanroom” (softwall) you don’t have to permit the install.
Fact – The uniform building code (UBC) states what has to be permitted and is interpreted by virtually all municipal building inspectors. The bottom line in our experience – if the room is 6’ tall and it holds people and equipment, it must be permanently adhered to the building floor, sprinklered and permitted. Many softwall or catalogs sell light duty, low cost systems that cannot be installed in California legally. Frames or supports must be California seismic zone 4 2001 UBC rated and wet stamped per project. Individual engineering drawing for your specific installation must be provided. We have customers who purchased catalog or out of state cleanroom kit systems, put them in without permits, got caught, then requested factory help and were promised these calcs forever – they never got them. We then had to go in, re-design the support systems, apply for permits, help customer pay penalties (advise), retrofit existing system (if possible) and obtain building inspections and a final inspection.

The quickest we’ve ever done this is 3 weeks, the longest 6 months. They were red-tagged and shut down while this process took place.

Comment
5. Fancy little shut off louvers protect your cleanroom if the power goes out or if you shut it down.
Fact – All cleanrooms leak. That’s why you have positive pressure. If you shut it off it can leak in as well as out. Why would you shut it down? To save on electricity?
O.K. let’s figure it out.
7 each fan filter units at 1.2 amps running x 110 volt = 1320 watts/hr
AXV = watt
1320
x 7 fan filter units
9247 watts or about 1 kw which costs you .15 cents or so.

So to shut off your cleanroom – for electricity for the fan filter units saves you about $1.05 per 8 hours or $2.10 overnight. But you must also add the additional heat load of about 1 ton A/C – still peanuts overall.

What do you loose when you shut your room down?
A. Positive pressure to keep particle intrusion to a minimum.
B. HEPA or ULPA filters work 4 ways – simply put

1. Impaction – Large to small particle sticks to media through pressure.
2. Sieving – Large to small particle gets strained and caught between media.
3. Vanderwalls forces – sub-micron particle gets stuck through electrostatic attraction.
4. Brownian movement – sub-micron particle wander into media and sticks.

I know that I just simplified 400 pages of physics into prose – but please bear with me.

If you shut off your filter you eliminate pressure against the media. The media relaxes and when you turn the unit on again you push particles through the media which were previously impacted by pressure. You literally dump thousands or millions of particles through the media into the room for several seconds until the medial recovers. This is the awful smell you get when you turn on a used filter unit after it’s been shut off. You may not smell it when the system is brand new – but you sure will smell it when you’ve used the system for a while.

Now – how does that affect your product?
Well realistically most of that airborne stuff is pushed out of the room through vents and probably will revisit the filter at some point. But some of the contaminants adhere to the surfaces of your room and must be cleaned by janitorial procedures (once a week wipe down – for instance). If you turn the system on and you stay out of the room for 15-20 minutes you should be O.K. And remember – the more HEPA filtration you have the quicker the room recovers. Also in line with this thinking, the more HEPA’s you have the more it costs to run them all the time and so it becomes much more attractive to throttle them back (special controller) or shut them off at night. But for $2.00 a night, Class 100,000, – sorry this doesn’t make sense to me.

Louvers help if the room is down – you loose power – But you know what – when turned back on I’d still run a janitorial procedure through the room – Takes 20 minutes and insures your product.

Comment
6. 7’ is O.K. for a cleanroom ceiling height.
Fact/opinion – get every inch you can. Talk about claustrophobia – especially if you are 6’-3” tall. Plus many racks and equipment are 7’ tall and with an additional 6” you can get them in the room and move them around.

Comment
7. Maintenance on fan filter units by going up through the cleanroom ceiling is O.K. Example – changing pre-filters.
Fact – Leaving pre-filters on the top of fan filter units in a tight installation is dumb. You got to violate the integrity of your room to get to them about once a quarter. You know what eventually happens – People don’t do it, the pre-filters clog, the HEPA eventually clog, the motors run hot and eventually fails. Remoting pre-filters away from the fan filter units by any of several methods has the following benefits.

A. The hottest spot in the room is above your cleanroom – That’s the air that the
fan filter units dump into your cleanroom if the returns and pre-filters are not
remoted.

B The dirtiest place in your support room eventually will be the top of your
cleanroom. No janitorial service works up there and eventually layers of dust
and debris will settle up there on the cleanroom ceiling right next to your fan
filter unit inlet – not smart.

C. Maintenance on fan filter units motor blowers or filter must be accomplished by under the ceiling moving or removing of entire fan filter unit assembly. This is complicated and dirty and should not be accomplished in an active cleanroom. However redundancy in design (a few extra fan filter units) and the super longevity of well maintained systems pretty well minimize this problem. This issue comes up much less frequently than regular maintenance of pre-filters of fan filter units.

D. Velocity adjustments
FS209E spec 90 fpm + 20%. Run your fan filter units up to mid range (750 cfm) and spec them at 650 and you won’t have to adjust them for several years in normal use. And with good pre-filter maintenance a good fan filter unit like Envirco MAC 10 units are sized with proper fan and motor engineering to allow higher speed (makes up for filter loading up) without lots of additional noise. That would be bothersome. Lower quality cheap fan filter units – when you turn them up – they howl. That’s because they have cheaper fans and motor which reach max. capacity sooner and the fan tips speeds now exceed proper design – thus the noise. Don’t get caught in that trap – buy the best fan filter units available – they’re only about $100.00 a piece more retail and that’s money well invested.

Comment
8. Light duty catalog softwall or hardwall rooms go together quickly – generally within a day.
Fact – Watch out – many of these systems are so light-weight and go together with minimum hardware that they become an absolute rattle trap within a year or so.
Buy quality that lasts?

Comment
9. Vinyl cleanrooms don’t need sprinklers.
Fact - Oh Boy – check out your UBC and call your fire department (you know those are the guys with the funny hats and cool trucks who drop by unannounced 2 or 3 times a year) no kidding. If you have sprinklers in your building many departments will shut you down if your modular portable room is not sprinklered. Then they flag the city building department which finds out you built without a permit and they red tag you and shut you down and then you call your catalog company for support and they don’t answer the phone (just kidding). By the way – seriously if you don’t pull a permit and it’s required anyone including vendors who are aware, insurance carriers, disgruntled employees, or competitors, etc. can at any time call the city, report you and get you shut down. Be careful. Also if you have a problem in a room, which is not permitted, you need to check with your attorneys for exposure to gross negligence suits.

Comment
10. Single pass softwall cleanrooms do not need air conditioning.
Fact – Here we go again. O.K. – probably a well installed modular room in a much larger A/C controlled environment will follow the other areas temperature and humidity fairly closely. The trick is to make sure that some of the larger rooms A/C supply gets to the inlet of the cleanroom fan filter units. About 30% of fan filter units in a class 10,000 and 50%-70% in a typical class 100,000 need some A/C.

Check this out
Typical office = 1.0 cfm/per sq. ft. cooling load.
Cleanroom – 600 sq. ft. x 8 = 4800 cu. ft. 600 cu. ft./min. cooling
Or 1 air change per 8 minutes
Or ¼ of the air flow of class 100,000 room typical
plus heat load
Add 2 tons or 800 cfm load total 1400 cfm cooling or almost 50% of class 100,000 air changes

Now – assuming that you can supply enough A/C to balance the room roughly with its additional heat load (equipment and people and fan filter units and extraordinary lighting) in the cleanroom – then you should be able to follow the main room fairly closely – within 2-5 degree generally the cleanroom is slightly hotter than the outside room – up 2-3 degree.

The real problem isn’t the above guess estimate which probably won’t drive you out the room if you mess up. The real problem is if you introduce:

A. Different or tighter control specs in your cleanroom than the support room and you try to get this handled by the same system. You can’t get tighter control. Also you can’t get humidity control from a system not designed for humidity control without upgrades.

B. Exhaust in the cleanroom – really, really messes up cleanroom balancing if not done well. One ton of air conditioning = 400 cfm. One wet station or fume hood 6’ long typically exhausts 800-1200 cfm or 2-3 tons of cooling

That air has to be made up someplace. Either though fan filter units drawing from support room or directly by-passed into the cleanroom. Now add the variable of turning the fume hood on and off – guess what? That’s when you need a real engineering look at your design. Also a major concern is extraordinary heat load within your cleanroom which requires more cooling that your fan filter units coupled to the support room can supply – ovens are a real good example of this issue. With proper engineering we can do things like bulk heading the equipment to put the majority of the heat source outside of the cleanroom or bypass supply and exhaust air to eliminate heat load while not affecting the cleanroom. Again engineering per your specific requirements.

Statement
Cleanrooms don’t have to be attached to the floor – especially roll around units on casters.
Fact – Roll around units at rest present the same or more hazard than free standing modular units which are not fastened down. The following agencies must have their say (partial list).

Building department
Safety/Haz Mat
Fire department
OSHA
Workers Comp
Liability Insurance

Better do your homework on this.

Finally - Comment
11. And this is not to insult company facilities managers – I know you know this –
This is to help you explain this to “the others”

A cleanroom is not a piece of equipment. It is a part of a facility. It interacts with the rest of the facility. It depends on the rest of the facility. It must be integrated into the facility and to do that properly – it requires engineering. Engineering is not spelt SALES.

The following disciplines are involved:

Mechanical
Engineering – all environmental controls and equipment. All plumbing and supply lines and drains.

Structural
Engineering – Building and or modular room for frame, roof and equipment mounting especially seismic.

Electrical Engineering
Electrical hook-up of mechanical systems, room electrical for 110 volt plugs (convenience wiring) special lighting (Title 24) and equipment wiring.

Haz Mat
Chemical storage, handling, safety, disposal, contaminant, etc.

Compliance
Government regulations, special licensing, etc.

Architect
Permits, integrated engineering into building plans called “As-Built” – they are electrical, structural, mechanical, plumbing, elevation views, architectural details, building plot plans, evacuation plans (important when planning cleanroom entrance and exit) out here like architect cleanroom design engineers. This person needs to understand your process, layout, work flow, special FDA, or other requirements and understands cleanroom protocols.
Also ADA compliance for handicap.

In addition to the above please review the list I’ve included of items of consideration and information necessary, in many instances, to provide a properly designed and minimally invasive cleanroom project.

Just a thought, I wouldn’t store my Lexus in an Army tent – why would anyone trust their sensitive products to a softwall cleanroom?