Isn’t it about time for some cleanroom lighting standards?

By George Ryder

Next time you enter a cleanroom, look at the ceiling and estimate how much ceiling space is dedicated to lighting fixtures. Each of those lighting fixtures is actually an enclosure that ultimately affects the cleanliness of your clean space.

With that in mind, it's imperative that each lighting enclosure be designed and manufactured with the same integrity that you demonstrated in the design and construction of your cleanroom or containment area. Consider that approximately 30 percent of your cleanroom ceiling consists of fixtures and the importance of this decision becomes a little more magnified.

Ask yourself the following question: How do I go about choosing lighting equipment that won't leak, introduce toxicity/corrosion, add excessive heat or create potentially unsafe conditions? Truth is, the onus should be placed on the lighting manufacturers. Suppliers should provide end users with equipment that is designed and produced in a manner that guarantees that the equipment will not create any of the negative conditions listed above.

In many cases, too much emphasis is placed on product features at the expense of product performance. Features imply, but never guarantee, performance; as is the case with all cleanroom equipment, there is no substitute for performance evaluation.

Never assume that features such as triple gasketing, one-piece door and caulked housing guarantee that the fixture will not leak. You must demand validated product performance—no leaks, no toxicity/corrosion, etc.

Let's concentrate on the process of identifying standards and performance criteria that address and articulate product performance that will protect the integrity of your cleanroom.

The key is to emphasize the importance of confirming specified product performance through independent testing laboratories. Let's assume the end user values and demands the following:

  • 1) Authenticity
  • 2) Universally acknowledged standards and criteria
  • 3) Measurable performance
  • 4) Performance confirmation by third party

Performance specification

The goal is to create a product specification of measurable performances to protect the integrity of your cleanroom and identify standards and criteria that address each product performance.

The lighting fixture:

1) Shall not leak
Standard—International Electrotechnical Commission (Degrees of Protection Provided by Luminaires)

Criteria-IP65—Ingress Protection (IP) is rated by two numbers. The first digit rates ingress protection from solid objects and the second digit rates ingress protection from water. The IP6_ denotes dustproof. During this test, the lighting fixture is placed in a dust chamber filled with circulating talcum powder. The fixture is allowed to reach its highest operating temperature and its lowest non-operating temperature. Following this test, the fixture is opened and inspected for any talcum penetration. The IP_5 protection from jet streams of water (3.3 GPM/.20-inch nozzle/8 feet from fixture/15 minute duration). The stream of water is directed at the most vulnerable points of the enclosure. Following this test, the enclosure is opened and the water-sensitive powder placed in the enclosure is inspected for any water penetration.

Independent Laboratory Confirmation—Underwriters Laboratory Inc.

2) Shall not introduce corrosion or toxicity to the clean space

Standard—National Sanitation Foundation International (Special Equipment and/or Devices)

Criteria—Splash/Non-Food Zone and Food Zone/Non Contact: These two criteria are similar with the exception that the second addresses lens material and the type of fasteners used to secure the doorframe of the enclosure. Both criteria state that both materials and design must assure neither toxicity or corrosion can be introduced to the area through the fixture. Material selection, design and fabrication techniques are very specific.

Independent Laboratory Confirmation—National Sanitation Foundation International

3) Shall be easily cleaned

The standard, criteria and independent laboratory confirmation are the same as #2.

4) Shall demonstrate high lumen efficiency

Standard—Illuminating Engineering Society (IES) Handbook

Criteria—Lumen Efficiency: The IES has defined the method for testing the photometric performance of lighting fixtures. In basic terms, the enclosure interior must be designed to transmit the highest percentage of the energy produced by the lamps to the area being illuminated. Since fixtures require ceiling space and lamps produce heat, the efficiency of the lighting fixture will have a dramatic impact on ceiling space available for air filtration and the amount of equipment and energy required to maintain the desired temperature of the cleanroom.

Independent Laboratory Confirmation—Independent Testing Labs (ITL)

5) Shall be safe in Class I, Division 2; Class II, Division 2 and Simultaneous Hazardous Locations applications

Standard—Electrical Code (National Fire Protection Association 70-2002)

Criteria—Class I, Division 2 (flammable gasses); Class II, Division 2 (explosive dusts); Simultaneous Hazardous Locations (both of the previous simultaneously); Emergency Lighting for Hazardous Locations (Internal emergency batter packs). Please note the Division 2 classification. This denotes that the hazardous material is present in abnormal conditions such as accidental spillage. This is not be confused with Division 1 classification, and also note that hazardous locations and zones have similarities and differences.

Independent Laboratory Confirmation—Underwriters Laboratory Incorporated

Guiding principals

The product performance specification listed above is just an example, but it's possible to expand the performance requirements, select alternate standards/criteria or choose other third-party confirmation. I believe that the undisputable guiding principals are:

  1. Focus on performance, not features, that produce the desired results.
  2. Identify existing acknowledged standards and criteria that articulate and quantify the desired performance.
  3. Confirm product performance with independent laboratory testing. Avoid factory confirmation of performance.

Product features that result in performance

The following are only guidelines for identifying lighting fixtures that will protect the integrity of your cleanrooms and containment areas:

  1. Structural integrity: Examine the housing body and doorframe. Use your professional abilities and common sense to evaluate the fixtures ability to protect your environment. Check the welding, examine the means of providing power and inspect the doorframe gasket.
  2. Material selection: Examine the gasket, identify the doorframe material and check finishes.
  3. Lumen efficiency: Check photometric reports to validate claims. You should expect efficiency in the 70+ percent range for 2¥4 lighting fixtures.
  4. Listings, ratings, certifications: Demand proof on the letterhead of testing facilities. Do not accept factory tests or “in compliance with” statements.

Lighting fixtures fill a lot of holes in your clean space. If they are not designed, tested and manufactured with the same integrity that you demonstrated in the design, building and maintenance of your environment, you are inviting unnecessary disaster.

Demand confirmed performance that protects the integrity of your clean space. III

George Ryder, vice president of Kenall Manufacturing Co. (Gurnee, Ill.), has been involved in the development of lighting systems for cleanroom applications for more than 15 years. He can be reached at [email protected].


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