![]() An exception being where a written hazard assessment indicates otherwise.įor purposes of establishing a value for the internal volume of the hood used in determining the flow rates corresponding to the desired value of hood air changes per hour, the internal hood volume is approximated and hereby defined as the total internal hood work surface area times the internal height of the hood.” Minimum hood flow rates might be selected within the above range if the user complies with provisions below*. When attempting to save energy in typically higher hood density installations, minimum fume hood flow rates in the range of 150 to 375 hood air changes per hour (ACH) have been used to control vapor concentrations inside hood interiors. Here is the exact verbiage from the new Standard: The new standard changes this from a cfm per square foot to an air change rate. This equates to around 250 cfm for a 6 foot hood. The previous standard called for a minimum of 25 cfm per square foot of fume hood bench area (work space). With the increased usage of demand based control of air change rates and the reduction of sensible heat loads in labs, the main driver in labs is now the required hood minimum ventilation rate. The biggest drivers of these outside air rates are the required hood minimum flows, thermal loads and air change rates. Due to their nature, labs require 100% outside air with no option for recirculation. The biggest driver of laboratory energy use is outside air. After years of testing here in the United States and a review of European practices, a new minimum fume hood ventilation rate has been established. This new Standard replaces the one issued in 2003 and has a huge impact when it comes to energy efficiency in labs. Laughable.After years of work, the new ANSI/AIHA Z9.5-2012 Standard for Laboratory Ventilation has been released. Lastly a fan noise profile for either the dBa across the same realm of speed %s is a nice to have.įranky the fact that you think that you have to explain what pressure is to me is insulting. At a bare minimum it would include a single curve for a 100% speed, but it would be far better to have fan curves for multiple speeds (0,10,20,30,40,50,60,70,80,90%). This would include pressure on one axis, flow on the other. What you need for accurately comparing fans is a basic pressure-flow curve at a bare minimum. Linearly interpolating between these two points is a failure in basic mechanical understanding, and if one of my team members did that I would fire them. This gives you at a very maximum 2 points on a fan curve. If the mfg includes a flow rate, it is almost certainly at a no back pressure condition (0mmH2O). Listing a maximum static pressure in the ad gives you a single point (at zero flow, deadheaded condition) of data. Static pressure (if listed in the ad) is absolutely a garbage statistic meant to try to sway buyers. I have been sizing mechanical equipment (pumps, blowers, HVAC) for 13+ years now for $50M+ of projects per year. Then your further reply trying to explain the very basics of flow and pressure bahahha. Oh goodness hahaha I needed a laugh this morning. Pick, Assemble and Install: Video Guide.No intentionally harmful, misleading or joke advice.No excessive posting (more than one submission in 24 hours).No selling, trading or requests for valuation.No self-promotion, advertising, begging, or surveys.No submissions about memes, jokes, meta, or hypothetical / dream builds.No titles that are all-caps, clickbait, PSAs, pro-tips or contain emoji. ![]() No submissions about retailer or customer service experiences.No submissions about sales, deals or unauthorized giveaways.No submissions about hardware news, rumors, or reviews.Please keep in mind that we are here to help you build a computer, not to build it for you. Submit Build Help/Ready post Submit Troubleshooting post Submit other post New Here? BuildAPC Beginner's Guide Live Chat on Discord Daily Simple Questions threads
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