E-news for the Construction Division Summer 2012

Cleanroom Construction Projects Offer Unique Challenges

Cleanroom construction is nothing new in the literal sense, dating back more than a hundred years to hospital environments. The process was later applied to industrial manufacturing during World War II as a means for safeguarding instrumentation during the production of munitions, tanks, and aircraft. However, the evolution of cleanroom construction and the expanded applications for these projects today have helped create a renaissance business, equal in stature to sustainable design and green construction.

The cornerstone of cleanroom development is, of course, the control of contamination, specifically airborne particulate matter that naturally occurs, such as dust, dirt, pollen, bacteria, and other microorganisms, even sea mist. Industrial functions, office activity, and workplace personnel, too, contribute significantly to airborne contamination, including particulates generated from combustion processes, chemical vapors, and friction in manufacturing equipment and contaminate particles emitted in the form of skin flakes, lint, cosmetics, and respiratory gases.

In most instances, the required standard of cleanliness of a room area depends on its purpose. Federal Standard 209E, considered the benchmark for cleanliness for many industries, defines a cleanroom as that in which the concentration of airborne particles is controlled to a specified maximum number of particles 0.5 microns in size per cubic foot (or cubic meter) of sampled air. Usually, cleanroom cleanliness is expressed in terms of classification areas or numbers, such as Class 100 or Class 100,000. For example, those classifications would denote there should be no more than 100 or 100,000 particles, respectively, larger than 0.5 microns per cubic foot of air during the sampling period.

The more susceptible a product or procedure is to contamination, the more stringent the FS 209E requirements become. And as technology advances, the purposes for cleanrooms increase, too. Aside from hospital health care, cleanroom construction has carved niches into numerous other industries: electronics, semiconductors, micromechanics, optics, biotechnology, pharmaceuticals, medical devices, and food and beverages.

Today, a substantial number of manufacturing or production processes require that area spaces be designed and constructed to control particulate and microbial contamination, while maintaining reasonable installation and operating costs. Not surprising, the key stakeholders in modern-day cleanroom construction have become the mechanical engineers who must design and build HVAC systems sophisticated enough to satisfy FS 209E requirements.

Professional Engineer Abraham Marinelarena, a specialist in cleanroom development and senior mechanical engineer for Bath Consulting Corp. in El Paso, Texas, notes that cleanrooms have evolved into two major types, differentiated by their method of ventilation—turbulent air flow and laminar air flow. The general method of ventilation used in turbulent air flow cleanrooms is similar to that found in general building and plant construction, with air supplied by an air-conditioning system through diffusers in the ceiling structure. However, a cleanroom differs from an ordinary ventilated room in three ways: increased air supply, use of high-efficiency particulate air filters, and room pressurization.

Laminar air flow, Marinelarena explains, is used when low airborne concentrations of particles or bacteria are required. This air flow pattern is in one direction, usually horizontal or vertical and at a uniform speed of between 60 to 90 feet per minute throughout the entire cleanroom area. The air velocity must be sufficient to remove relatively large particles before they settle onto surfaces and must take into account practical situations, such as room obstructions and personnel moving around. Any contaminant released into the air can be immediately removed by laminar air flow, whereas turbulent air flow ventilation relies on mixing and dilution to remove contamination.  

Although air flow design is critical, Marinelarena emphasizes that it alone does not guarantee that cleanroom conditions will be satisfied. “Construction finishes, personnel and clothing, materials and equipment, and points of egress are other sources of particulate contamination that must also be controlled,” he says. In particular, room construction and material finishes are a significant part of cleanroom design, he points out, because not only is it vital to exclude outside contaminants, it is also important that material finishes not contribute to particle generation in the cleanroom space itself.  

Benchmark Engineering Group Inc. of Toledo, Ohio, recognized cleanroom consultants, also stresses the importance of carefully selected construction materials and products that meet cleanroom standards, including walls, floors, ceiling tiles, lighting fixtures, doors, and windows. Benchmark’s clean construction guidelines cite the maintenance of ventilation as paramount, noting, “Contamination of the existing house ventilation can be prevented by isolating supply air dampers in the construction areas to prevent a positive pressure within the construction space.” Maintaining construction in a state of negative pressurization should always be the primary goal.

“A cleanroom requires the highest standards of construction,” says Space Industries Ltd. of Christchurch, England. “The construction materials used to build cleanrooms can differ greatly from those used in non-cleanroom construction.” For example:  

  • A cleanroom should be built with an airtight structure.
  • The internal surface finish should be smooth and suitable for cleaning.
  • The internal surface finish should be sufficiently tough to resist chipping or powdering when impacted or abraded.
  • Some process chemicals, cleaning agents, disinfectants, and water may attack or penetrate conventional finishes.
  • In some cleanrooms, electro-dissipative construction materials will be required.
  • In some cleanrooms, construction materials that give a minimum of “outgassing” will be necessary.  

Additionally, materials that are used for cleanroom construction should be smooth on the surface facing the inside of the cleanroom, and all butts and joints as seen from the inside of the cleanroom should not show openings that may harbor, and then disperse, dirt.  

All cleanrooms, as expected, have their own specific protocols for construction and operation. When designing and constructing a pharmaceutical cleanroom, for instance, the International Journal of Pharmaceutical Compounding says several critical factors must be considered, such as policies and procedures, employee training, aseptic technique and process validation, ongoing environmental monitoring, facility maintenance, and compliance auditing. If these factors are not properly addressed, problems of quality, operation, or maintenance will result. It is often suggested that professional independent consultants be retained who can serve as project managers for constructing cleanrooms for specific industries.

Happenings on the Hill

  • NSPE joined an international group of engineering societies in endorsing the U.N.'s "Sustainable Energy for All" initiative. The program seeks to ensure universal access to modern energy services, double energy efficiency rates worldwide, and double the share of renewable energy in the global energy mix by 2030.
  • The USA Science & Engineering Festival was held in Washington, D.C., in April. NSPE was a festival partner and sponsored a booth featuring an engineering activity where children and parents built catapults for launching Ping Pong balls while learning about engineering design and simple machines. The festival has gained the support of the president and has an honorary congressional host committee of 22 senators and 73 representatives.
  • NSPE met with representatives from the Society of Afghan Architects and Engineers. SAAE President and Kabul University professor Jamil Khalid, Afghanistan Ministry of Public Works procurement officer Dalia Akbarmir, and ManSab International Vice President Ahmad Wali Shairzay discussed the challenges of organizing an association for design professionals.

    SAAE was founded by a group of Afghan architects and engineers in 2005 to advance the architectural, engineering, and related professions through high standards of professional practice and ethical conduct. The organization seeks to help build capacity in Afghanistan through training and education to meet the present needs of reconstruction and the long-term needs of sustainable development.

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The Role of the Consulting Engineer: Construction Contracts

The prime design engineer often is required to provide plans and specifications to contractors for bidding purposes. To do so, the professional engineer should understand the contract provisions as included in the specifications. There are acceptable procedures for prequalifying bidders, evaluating bids, and awarding construction contracts.

Although the contractor typically will contract for the work directly with the owner, the engineer may be the owner’s representative in all areas of negotiation with the contractor. That exposes the engineer to liability for the accuracy and completeness of actions taken on behalf of the client. The construction contract assigns to the contractor responsibility for safe construction practices and for work safety at the job site.

During construction, the engineer should be retained to make periodic job site visits to observe the progress and quality of the various aspects of the contractors’ work. Site visits have two general purposes. One is to confirm that the contractors’ work adheres to project plans and specifications. The other is to confirm that progress is on schedule and to approve periodic progress payments. The exact nature and purpose of each of these responsibilities should be spelled out clearly in the Owner Engineer Agreement for Professional Services. It is not the responsibility of the engineer or the owner’s representative to direct, supervise, or have control over the means, methods, techniques, sequences, or procedures of construction selected by the contractor. In other words, the engineer should never instruct the contractor in how to do or what to do.

The services of an engineering firm that specializes in materials engineering and materials testing may be required on a project. That is an engineering function that is necessary on some projects in order to make engineering calculations and judgments relative to the adequacy of construction. Not only do the degree and quality of the testing influence the quality and service ability of the end product for the owner, they also provide some liability protection for the prime design engineer and can help confirm that the structure is built to the plans and specifications.

Most courts have held that the contractor is responsible for constructing the project in conformance with the plans and specifications. But all experienced engineers know that problems of constructed projects normally are not the result of a simple omission, but of a complex series of oversights, omissions, failures to comply, and breakdowns or delays in communications. Comprehensive construction testing and observation of the contractors’ work on behalf of the owner and engineer often will prevent these problems from developing.

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NSPE Education On Demand

Learn how to communicate more clearly, both verbally and in writing. Find out how to cut costs and take better control of your bottom line. Learn more about how to approach decision making in an ethical manner, and how the history of these decisions can give you perspective on your own challenges. Finally, get your ethics requirements covered by the authority on the subject.

Each of our archived Web seminars is $69 for nonmembers and $35 for members.

Visit our Web site to see a full list of our archived seminars. [ return to top ]

NSPE Aims to Define Body of Knowledge

NSPE leaders are in the beginning stages of drafting a document that will detail the knowledge, skills, and attitudes that are necessary for practice as a professional engineer.

NSPE's Engineering Body of Knowledge, once adopted, would serve as a formal statement on the level of achievement professional engineers should demonstrate in various topics and skills. While other organizations have developed discipline-specific bodies of knowledge, NSPE's BOK would aim to be applicable to all engineering disciplines. The multiyear effort is being led by NSPE's Licensure and Qualifications for Practice Committee.

The first draft of the NSPE Engineering BOK covers three areas: guiding principles affecting practice as an engineer in the future, key attributes of the engineer of the future, and outcomes. Once the draft has been reviewed internally and comments have been received, informal comments will be sought from other engineering organizations.

Read more in the blog posting "NSPE Engineering Body of Knowledge Outline: First Draft."  [ return to top ]

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