Consulting-Specifying Engineer - October 2008 - (Page 21)

M/E Roundtable to be reduced when the hood is not in use or the lab is unoccupied. Designers need to beware of fume hoods located in labs that will operate 365/24/7 and are governed by ACH, as incorporating VAV controls on these hoods will increase initial system cost and will not reduce energy consumption. Another effective approach is to have the BAS monitor fume hood airflow and/or sash heights. This allows building owners to monitor whether their staff is lowering fume hood sashes. On projects where fume hood airflow is controlled using pressure controls, the CFM can be trended and correlated to an average sash height. On projects where potentiometers (sash height sensors) are used to control airflow, the sash height can be trended directly and averaged over time. This could be trended on a hood-by-hood or lab-by-lab basis so that problem areas can be easily identified and corrected. Feliciano-Welpe: Bar none, the safest, most energy-efficient use of a fume hood is a VAV-controlled fume hood with a closed sash. Implementation of a sash management program is paramount to encouraging good lab practices and the safety of the users. A closed sash can protect a worker from volatile reactions within a fume hood. The fume hood is a safety device. 2-state control of constant volume or low-flow hoods can also be energy-efficient with the use of a sash position switch incorporated into a sash management program for safety. The BAS can be used for a sash management program by trending the position of the sash. We have several customers that have used this information very effectively as part of an annual safety training class. CSE : What codes and standards actions in 2008 should engineers be aware of? Hanegan: Engineers working on hospital pharmacies or similar work should be aware that the United States Pharmacopeia has updated standard 797 on Pharmaceutical Compounding – Sterile Preparations. ASHRAE is currently in the process of updating its Laboratory Design Guide, which was originally published in 2001. Also, ASHRAE recently published Guideline 4, in 2008, called Preparation of Operating and Maintenance Documentation for Building Systems; and Standard 180-2008, Standard Practice for Inspection and Maintenance of Commercial Building HVAC Systems. Brooks: AMCA International has recently completed developing a laboratory method of test standard and certified ratings program for induced flow fans. The standard, AMCA 260, Laboratory Methods of Testing Induced Flow Fans for Rating, was written in response to laboratory ventilation industry needs for third-party performance ratings. The standard includes a method to determine the outlet airflow (induced flow) of an induced flow fan. The certified ratings program includes inlet airflow, outlet airflow (induced flow), power, efficiency, and outlet size. CSE : What are the most serious design c hallenges for lab ven tilation systems? What keeps a lab designer up at night? Bar none, the tored, but on consumption of carbon, which must be periodically tested. I also worry about construction quality when I am not at the jobsite. This includes welding of stainless steel ductwork. My experience has been that even welding done by certified welders needs to be carefully observed and that the ductwork needs to be rigorously leak tested. Another concern: Construction of lab rooms and sealing of leaks. A leaky room makes it difficult to maintain pressure differentials. Each building is a prototype full of complex systems that have not been fully assembled and tested before. Owners expect us to be innovative and perfect at the same time. I try to be innovative but worry about the perfect part because I’m human. Quality control on construction documents is really important, along with understanding and communicating owner expectations. Sprangers: It is often difficult to determine exactly what an end user is going to be doing in a fume hood or lab, so more often than not conservative assumptions safest, most energy-efficient use of a fume hood is a VAV-controlled fume Tsimanis: The pressur- hood with a closed sash. ization control within the lab space is a critical design requirement. The airflow should be designed to minimize chemical smell and to provide the desired space containment. The emergency ventilation can be designed with many different strategies. The challenge in the design is to create a safe escape opportunity for the occupants in event of an emergency. Hanegan: Trying to design exhaust systems without the benefit of airflow modeling. I am always trying to sell owners on the valuable results that modeling provides over hand calculations, particularly on buildings with complex geometries, to reduce the likelihood of exhaust air being re-entrained into a building. The next is educating owners and contractors about how to properly replace and leak test HEPA filters and carbon adsorbers. Carbon adsorbers are particularly challenging because they are not changed based on pressure drop, which can be continuously and cheaply moniare made that can increase initial system cost and/or energy costs over the lifetime of the labs. Determining ACH is a prime example. Four to 12 ACH is a very common range that laboratories fall into or will be designed with, but there are labs that operate with 8 and actually need 15, or operate with 12 and only need 6. For areas governed by the International Mechanical Code, it can also be difficult to determine whether a system or portion of a system needs to be classified as a hazardous exhaust system. Having a common and documented understanding between the owner, users, design team, and local code authority is a critical step to ensure that the system will not be over- or under-designed and/or get rejected during a code/permit review. Feliciano-Welpe: Ensuring that the air balance for pressurization has been properly calculated. Designers can only use their best guess for the makeup air (offset) required for maintaining the lab negative (or posi- Consulting-Specifying Engineer • OCTOBER 2008 21

Table of Contents Feed for the Digital Edition of Consulting-Specifying Engineer - October 2008

Consulting-Specifying Engineer - October 2008 Contents Viewpoint Letters News M/E Roundtable Cities Under One Roof Eight Design Tips for Integration Is 'Green' Really New? Down the Drain Product of the Year Awards Codes & Standards Case Study New Products Equipment Lifecycles Advertiser Index Green Space

Consulting-Specifying Engineer - October 2008

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