What Do Particle Counters Mean?
TECHNICALPAPERWhat Do Particle Counters Mean?Version 01. Rev 01. September 2005
Info Overload: What Do My Particle Counts Mean?know, other than the U.S. Environmental ProtectionAgency’s PM2.5 and PM10 (mass concentration), there areno standards for particulate levels in the IAQ industry. Thisis due in part to the nature of airborne particulates, and themany influences that man and nature play in particulategeneration and movement.Particle Counter TerminologyThere are different types of particle counters –handheld, portable and remote. For ease of portability, Igenerally use a handheld instrument during IAQinvestigations. When using particle counters, one needs tobe aware of certain terms or phrases that are commonlyused when describing functions of the instrument, or howthe data is viewed and reported. Data are displayed in eitherCumulative or Differential mode. When viewing the data inCumulative mode, the number (counts) associated witheach channel size is the number of particles that theinstrument counted for that size and greater.Jim AkeyInside Sales – Eastern U.S.Lighthouse Worldwide SolutionsMedford, Ore.What is the difference between an orange?You may be thinking, what kind of question is that?Different than what?Common sense, and a decent background in theEnglish language, tells us we need to compare the orange tosomething else to determine any differences.One of the most common questions I am askedregarding particle counters pertains to the values, or particlecounts, the instrument just recorded. I am often asked, “Jim,I just took a sample with my new particle counter. I got40,000 counts at 0.3 µ (microns). What does this mean? Isthat good or bad?”My typical response to this question is that one set ofdata, in and of itself, means very little. Kind of like thequestion I posed earlier regarding the orange. Unless wecompare the particle counts to a baseline of previouslyrecorded counts, the new set of data has little value. As weFigure 1Figure 1 shows that 5,380 particles were 0.3 µ indiameter and greater; 3,260 particles that were 0.5 µ indiameter and greater; 2,572 particles that were 0.7 µ indiameter and greater; and so on.If the data are being viewed in Differential mode, thenthe counts associated with each channel size would indicatethe number of particles that are at least that micron size inThis article is reprinted from Volume 6, Issue 11 (September 2005)of Indoor Environment Connections newspaper.For subscription information, visit www.ieconnections.com.
Table 1diameter, up to, but not including the next size. Using thedata above (if sampled in Differential mode), we would seethat there are 5,380 particles that are between 0.3 µ and0.499 µ; 3,260 particles that are between 0.5 µ and 0.699 µ;2,572 particles that are between 0.7 µ and 0.999 µ, etc.Data format is also an important idea to understand.Some handheld particle counters display the data as eitherraw (actual number of particles counted for the time orvolume being sampled) or normalized (generally used whencertifying or verifying cleanroom classifications).Regardless of the sample time or volume, the count resultsare displayed in particles per cubic foot or cubic meter. If aone-minute sample is taken (0.1 cubic feet per minute), thecounts are multiplied by 10 to give the results in particlesper cubic foot; this is done to meet the cleanroom standardsrequirement of particles per cubic foot (Federal Standard209e) or particles per cubic meter (ISO 14644-1). (Thesestandards are explained in further detail later in this article.)Most particle counters allow you to select a sampletime or volume for each sample. Handheld particle countersare generally set to sample 0.1 CFM. I would suggest thatyou sample for at least one minute; this ensures that youtest enough air to give a representative idea of what ishappening in the area being sampled. Often, I will takethree samples at each location and use the average of thethree counts.Many particle counters allow you to assign locationnumbers to your samples. Changing location numbers whenyou sample in different areas assists in keeping the data in alogical order. Each time you move the particle counter,change the location number. This, combined with atimestamp including the date, will ensure that your data arerepresented clearly and concisely.Table 1 shows a sample download of some countstaken in seven different locations around our office. Datawere gathered in Cumulative mode, and the counts are inThis article is reprinted from Volume 6, Issue 11 (September 2005)of Indoor Environment Connections newspaper.For subscription information, visit www.ieconnections.com.
raw format. Figures for temperature and relative humidityare also included. Three samples were taken at eachlocation, and an average was provided for each set of data.Also, note that the counts taken outside are higher than anyof the samples taken indoors.The counts in Location 7 are extremely low. This areais a laminar flow hood, and is where sensors for our particlecounters are manufactured. Also, notice the counts that are1.0 µ in diameter and greater. Outside, there were anaverage of 2,289.3 counts at 1.0 µ and greater (whichequates to 22,893 counts per cubic foot). If any of the othersix locations were to have that many counts, I would havebeen concerned, as this indicates the possibility of activemold growth. As you can see, none of the other locationswere within even 50 percent of this – the closest being themen’s room at 32 percent!Particle Counters Used in an IAQ InvestigationNow that we are familiar with particle counterterminology, let’s focus on how a particle counter can assistus with our IAQ investigations. As we know, particlecounters offer immediate results that define the number ofparticles present in the sample volume, as well as a sizedistribution. Each individual IAQ professional candetermine his or her own sampling methodology, but each“plan” should contain a few basics.First and foremost, when sampling in either aresidential or business setting, particle counts should betaken outside the building. These readings will be the startof our baseline against which we will be comparingsubsequent counts. In an ideal situation, the particle countsoutdoors will always be higher than the readings gatheredinside. Isn’t that one of the reasons we live in structures – tobe protected from the elements? However, in manyinstances, the level of airborne particulates inside is greaterthan outdoors. This can be construed as our first indicatorthat something may be amiss.Secondly, take samples throughout the structure,paying particular attention to areas of concern from theresidents, or where a previous water intrusion is evident.This is establishing your baseline further. My experienceindicates that the more samples taken, the more statisticallyvalid your results will be. As we are aware, mold spores aregenerally between one and 10 µ in diameter. Pay closeattention to these channels, as this will be an indicator thatmold may be present in the vicinity.Once an area of concern has been discovered (elevatedcounts at one micron and greater), additional sampling is inorder. By taking multiple counts in various locations, onecan start to pinpoint the source of the problem. Traditionalsampling methods (Air-O-Cell cassettes, swab sampling,etc.) should be used to determine the types of mold, omThere are a number of industries outside the IAQprofession that require manufacturing to be done in a clean,controlled environment – commonly called cleanrooms.These are specially designed areas where temperature,humidity, airborne particulates, differential pressure,electrostatic discharge, airborne molecular contamination,and other factors are all closely monitored and controlled. Ithas been proven that excess particulate matter will have anegative effect on product yield for manufacturers ofsemiconductors and disk drives. For the chnology,industries, the Food and Drug Administration requires thatall devices and drugs be produced in a controlledenvironment.As alluded to earlier, the two cleanroom standardscurrently being used in the United States are the FederalStandard 209e and ISO 14644-1. Standard 209e is beingreplaced by the newer ISO 14644-1 standard, but about 60percent of our customers are still using it.In both standards, there are different classifications ofcleanrooms denoting the cleanliness level. For Standard209e, the classifications are Class 1 (the “cleanest”designation), Class 10, Class 100, Class 1,000, Class 10,000and Class 100,000. For the ISO 14644-1, the classificationsare ISO 1 (cleanest), ISO 2, ISO 3, ISO 4, ISO 5, ISO 6,ISO 7, ISO 8 and ISO 9.For each classification, there is a maximum number ofparticles allowed at certain sizes per cubic foot (Fed 209e)or cubic meter (ISO 14644). Each standard has a detailedprocedure that must be followed to determine the number ofsampling locations, how many samples must be taken ateach location, and the minimum volume of air that must besampled at each location. All counts are taken usingCumulative mode, and are reported in either particles percubic foot or particles per cubic meter. Table 2 shows theassociated number of particle counts allowed for eachclassification.Often, we can compare the particle counts we gather tothese standards. If we were to use just particle counts, thenmy desk would meet the classification of a Class 100,000cleanroom as there were 63,760 counts at 0.5 µ and greater.(An average of 6,376 counts for 0.1 CFM is multiplied by10 to demonstrate 63,760 particles per cubic foot.) Thistype of comparison can be done for your customers asanother way of explaining particulate levels.Assessment, Cleaning & Restoration of HVACSystemsAnother common use of handheld particle counterspertains to the National Air Duct Cleaners Association’sACR 2005 standard. Chapter 2, on particle-profilingThis article is reprinted from Volume 6, Issue 11 (September 2005)of Indoor Environment Connections newspaper.For subscription information, visit www.ieconnections.com.
Table 2procedures, details how the use of a particle counter canassist in ascertaining the levels of respirable and countableparticles in the HVAC system. This value can then becompared to the expected particle removal efficiency of theair filters in use. NADCA states that the results obtainedfrom this procedure are then used to “determine if certainsources of contamination are likely originating from withinthe HVAC system, and are subsequently contributing theseundesired agents or particles to the indoor ambient air.”Some duct-cleaning companies are also using handheldparticle counters to ensure proper cleaning of the HVACducts have been performed. Particle counts are takenthroughout the ductwork prior to cleaning. Cleaning isperformed, and the same locations are again sampled.Obviously, we hope the particle counts are substantiallylower after this process. I have assisted in this type ofsampling in the past, and was pleasantly surprised at thedifference in particulate levels after cleaning. In one sectionof the ductwork, an 80 percent decrease in particulate levelswas observed.Particle Counts vs. Traditional Sampling MethodsI am often asked if there is a correlation betweenparticle counts and data gathered by the more traditionalsampling methods. To my knowledge, no one hasperformed this type of testing and published their findings.However, many of the IAQ professionals that I work withare convinced that there is indeed a correlation.Within the past couple of months, I have initiated aprogram within the industry to compare particle counterdata with lab results. When gathering samples for lab work,particle counts are taken in the same location and for thesame time duration. Data are being logged and compared tothe results provided by the labs. Upon completion oftesting, I will report our findings to the industry.ConclusionThroughout this article, I have used some form of theword “compare” many times. As we have seen, when usinga particle counter in your investigation, we need to firstestablish a baseline and then compare subsequent readingsto this baseline. Whether comparing particle counts to abaseline or to another industry’s existing standard, the datagathered can be of great assistance in determining sourcesof airborne particulates.Jim Akey is responsible for inside sales with the stateof-the-art manufacturing facility of Lighthouse WorldwideSolutions, a recognized leader in the design andmanufacturing of aerosol particle counters. Akey holds abachelor’s degree in business and has 20 years experiencewithin the electronics and scientific instrumentation fields.He has participated in numerous IAQ investigations. Apresenter at the National Air Duct Cleaners Association’stechnical seminars, he is an active member of the IndoorAir Quality Association. Akey can be reached by e-mail atjakey@golighthouse.com or by phone at (541) 770-5905.This article is reprinted from Volume 6, Issue 11 (September 2005)of Indoor Environment Connections newspaper.For subscription information, visit www.ieconnections.com.
associated number of particle counts allowedfor each classification. Often,we cancompare theparticle countswegather to these standards. If we were to usejust particle counts, then my desk would meet the classification of a Class 100,000 cleanroomasthere were 63,760 counts at 0.5 µ and greater. (An average of6,376 counts for0.1 CFMis multiplied by
Introduction – COUNTERS A counter is a register that goes through a predetermined sequence of states upon the application of clock pulses. Asynchronous counters Synchronous counters Asynchronous CountersAsAsynchronous Countersynchronous Counters (or Ripple counters) the clock signal (CLK) is only used to clock th
10 ppb of 5 micron particles will have a lower NTU . The Rise of Particle Counters Two major crypto outbreaks in the US occurred in the early 90’s which led to intense interest in particle counters in the drinking water industry as a way to hep guard against future . Rapid. Incline. End
ISO 21401-4 Calibration. Abstract Airborne Particle Counters are widely used in Cleanrooms to monitor for signs of cleanroom air contamination and in most cases the particle count data is used to make critical process decisions. Today’s Portable particle counters have come a long way with the advent of laser
the need for ISO 21501-4 compliant particle counters in cleanroom certification and monitoring applications. Section B.2.2 of the previous standard, ISO 14644-1:1999, required particle counting to be performed using . The Lasair III Aerosol Particle Counter and the IsoAir 310P Aerosol Particle Sensor use a sophisticated system described .
1 Elec 326 1 Registers & Counters Registers & Counters Objectives This section deals with some simple and useful sequential circuits. Its objectives are to: Introduce registers as multi-bit storage devices. Introduce counters by adding logic to registers implementing the functional capability to increment and/or
restrooms, must comply. OFFICE Sales Counters (§227) Access is required to at least 1 of each type of sales counter provided. If counters are dispersed throughout a facility, accessible counters also must be dispersed. Employee Work Areas (§203.9) Partial access is required to areas used only by employees for work (worker side of sales counters,
counter with 3-state output registers, designed for 2-V to 5.5-V VCC operation. The counters have dedicated clock inputs. The counters share a clocked storage register to sample and save the counter contents. Both counters share an asynchronous clear input. The 32-bit storage register can be mapped on the output bus 8-bits at a time.
gathered in a traffic study, but one of the most important is the information gathered by the fixed-type automatic traffic counters. In North Dakota, five IBM model 3900 traffic counters were installed in 1936. In succeeding years, additional counters were installed and by 1961 there were 34 fixed
