Frequently Asked Questions

Questions here are our most frequently asked, and include topics on sampling media, methods, regulatory standards, and lab reports. Take a look for your question; it may be answered here. Or, you may also click here to Contact Us. The contact page contains categories of questions and the associated email addresses for a response.

Click here for a complete analyte list of Chemicals you can monitor on Badges.

 

Web Store Sampling Media Lab Reports Methods Technical Inserts Regulatory Standards

Sampling Media:

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Methods:

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Regulatory Standards:

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Technical Insert Questions

AT Lab Report - Frequently Asked Questions

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Did not see your question?  Call us at 800-833-1258 ext 2 or email askassay@assaytech.com.

 

Sampling Media:

Are diffusive badges recommended for compliance sampling?

Yes. All Assay Technology personal monitors meet and/or exceed the OSHA accuracy and precision criteria for sampling and analytical methods. Samplers have been validated for performance under a wide variety of sampling conditions. For more information, please refer to our Validation Reports, which contain details on the design rationale and validation criteria.

Which chemicals may be sampled with the Assay Technology diffusive badge?

Diffusive samplers are available for a wide variety of vapors, including over 150 Organic Vapors, Amines, Aldehydes, Nitrous Oxide, Mercury, Acetic Acid, Ozone, Ammonia, and others. For a complete listing of chemicals, and the appropriate badge for sampling, please refer to our Industrial Hygiene Sampling Guide, diffusive sampling columns.

What is the highest flow rate that can be used for sorbent tube sampling?

Typically, flow rates for sorbent tubes range from 2 - 200 ml/min, with maximum flows not to exceed 1 L/min. However, the highest flow rate will be dependent on the type of sorbent used, the sampling environment, anticipated concentrations, and any possible interferences. See the selected sampling method for information on the maximum flow rate and breakthrough volumes.

How do I know how much of a chemical can be collected on a sorbent badge or tube?

NIOSH has defined sampler capacity as two-thirds of the experimental breakthrough capacity of the solid sorbent, for gases and vapors. Sampler capacity is a conservative estimate of the total mass of chemical that can be absorbed on the sampling media, without loss or overloading. Use the sampling method to determine the working range in ppm and ug per sample. This will give you an approximate range for capacity.

Why are blanks required by the lab for each set of sampling tubes or cassettes I submit?

  • Media Blanks:  Since Assay Technology does not manufacuture this media, nor does it analyze this media regularly, we require the customer provide a blank with their samples to be added or a blank will be added for them so the background, if any can be corrected for.  However, if the customer provides a Field Blank, the laboratory will analyze a media blank, free of charge.
  • Field Blanks: The use of field blanks to monitor and correct for any background comtamination that may have occurred during storage, handing or shipping is recommended.  Unless requested, the laboratory will not Field Blank correct results.  

Are blanks required by the lab for the analysis of Assay Technology personal monitors?

  • Media Blanks:  It is not required that customers submit blanks when using Assay Technology badges.  The laboratory is always analyzing our own badges, we will automatically analyze a blank monitor with every analytical batch and blank correct as appropriate. 
  • Field Blanks:  The use of field blanks to monitor and correct for any background comtamination that may have occurred during storage, handing or shipping is recommended (especially for the Nitrous Oxide badge, 575). 

Are colorimetric tubes recommended for compliance sampling?

While detector tubes are an efficient tool for screening purposes or field surveys, most do not offer the specificity required to ensure measurement of exposures to a single chemical. In addition, most detector tubes do not meet the accuracy and precision criteria for sampling and analytical methods, as set forth by OSHA, of +/- 25% of the true value, at a 95% confidence level, at the PEL

How do I know which media to use for sampling specific chemicals?

Please refer to Assay Technology's Industrial Hygiene Sampling Guide for a complete listing of chemicals, and appropriate sampling media. Guidelines are based on OSHA and NIOSH sampling methods, and include media types for both diffusive and active testing.

Where can I send my samples for analysis by an AIHA-accredited lab?

In addition to being a manufacturer, Assay Technology operates two full-service, accredited industrial hygiene laboratories: Accreditations / Sampling Guide

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  Questions about Methods

Can I use sampling methods, other than those recommended by OSHA, NIOSH, or other government agencies?

Yes. OSHA does not require, or mandate, the use of a particular sampling method. Rather, OSHA and NIOSH set forth criteria for the accuracy and precision of sampling and analytical methods. An employer is obligated to select a method that meets these criteria, relative to their specific sampling conditions. Typically, these criteria for sampling at the permissable exposure limit, must be within +/- 25% of the true value, at a 95% confidence level. Alternative methods, with supporting validation data to demonstrate the accuracy and precision of the methods, are acceptable for OSHA compliance monitoring.

How do I determine which sampling method is better to use?

When multiple methods are published by OSHA and NIOSH, the user should consider a number of criteria, specific to the sampling situation. These include type of media preferred, analytical method, detection range, and any possible interferences. Talking with your laboratory is recommended, to address other limitations or advantages of one method over another. Generally, the more current the method, the better, in that problems of earlier methods have been corrected.

Are the sampling rates listed in methods exact, or can I sample at variable rates?

Most methods list an acceptable range of both sampling rates and air volumes that would apply to the majority of sampling situations. Staying within these ranges is recommended to ensure the validity of the method. When variations are made, quality control data points should be obtained to demonstrate the validity of the method under the new conditions.

How can I get copies of air sampling methods?

Both OSHA and NIOSH have sites devoted to their sampling and analytical methods. You may click on either of these links to reach those sites. You may also refer to the Assay Technology Industrial Hygiene Sampling Guide for a complete listing of chemicals, sampling media, flow rates and sample volumes.
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Questions about Regulatory Standards

What is an action level?

An action level is defined by the related OSHA standard for a specific chemical, and, typically, is one-half the permissable exposure limit. If an exposure is at, or exceeds this concentration, then some type of corrective action is required. The corrective actions are detailed in the OSHA standard for a specific chemical.

What is the recommended method for sampling a ceiling exposure limit?

A chemical having a ceiling limit shall, at no time, exceed the exposure limit given for that substance. Instantaneous monitoring is frequently not feasible. In these cases, the ceiling should be assessed as a 15-minute time weighted average exposure, which shall not be exceeded at any time during the day.
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Technical Insert Questions

What does sample capacity mean?  What is ppm-hr?

Sample Capacity is a measure of the amount or exposure of contaminant that a Sampler can collect without becoming saturated with leads to a biased low result.

Sample Capacity is often stated as the number of micrograms of a particular Contaminant that can be collected on a particular Sampler.  For the field IH practitioner, an equivalent (and more meaningful) expression of exposure can be derived by stating the contaminant concentration multiplied by the number of hours of sampling that can be conducted at that concentration.  In the Laboratory, the total contaminant exposure (in ppm-hour)  is computed from the Sampler’s contaminant loading (in microgram) from an equation using empirical constants.  The contaminant concentration (in ppm) reported by the Lab is computed from the exposure (in ppm-hr) divided by the exposure time (in hr).   Thus, Sample Capacity can be expressed either in “micrograms” of contaminant or in “ppm-hr” of contaminant exposure.    

Hence, the statement:  “The Sampler is able to sample at least 10 ppm for at least 8 hours (80 ppm-hr) without becoming saturated.”

 Testing to confirm the Sample Capacity is usually conducted by exposing the Sampler in a chamber to specific contaminant concentrations (ppm) and times (hr).  As long as the plot of “micrograms contaminant found” (on the Sampler) versus “ppm-hr” (of contaminant exposure) remains linear, that amount of exposure (whether in ‘micrograms” or “ppm-hr”) is understood to be within the Capacity of the Sampler for that Contaminant.  In many cases, the Sample Capacity has been stated as “greater than” ( > ) the highest contaminant exposure that has been verified in the lab.  In these cases, the actual Sample Capacity may be much higher than the value in the table.

The Sample capacity is listed on the technical inserts that come with the product and can be found on the website.  Technical Inserts

 

  Questions about Lab Reports  -  Example Report

  Has the Report Format Changed?

Yes.  Starting with samples received October 28th. 2013, we switched over to a brand new, custom built Lab Information Management System (LIMS).  The format and content of the reports was adjusted to more clearly meet AIHALAP, LLC (ISO 17025) requirements, while keeping in mind the feedback from customers we have received through the years.  Changes include:  Bigger Font, Regulatory Limits on the report (unless a customer requests them to not be present), three sample identification fields, and shading to more easily distinguish between samples.  For assistance with the new reports, please see the FAQs below or contact us by email (custservice@assaytech.com) or phone (800-833-1258 Option 2).

  Do I need a hard copy of the report mailed to me?

No.  Previously, only draft reports were emailed or faxed automatically.  The only official versions of the reports were the reports printed on letterhead and mailed.  With the new LIMS, the reports emailed and or faxed are official copies of the report since they are on company letterhead.  That means customers no longer need to be mailed hard copies of the reports.  For all the options, including an Excel readable summary of your data, contact our customer service.

  I did not receive my report. 

In the past, final copies of reports were mailed, but now the final copy of our reports can be emailed as a pdf.  Customers will receive their final copies faster than ever.  However, if a confirmation of receipt or report is not received, there could be a few issues that must be resolved.  Reports are sent by custservice@assaytech.com.  It is possible some email servers will see emails, with attachments, from this email address as potential SPAM and will put these emails into a Junk folder.  If a report is found in a Junk folder, the email server will have to be told to allow emails from this account.  Please contact your IT administrator.  Otherwise, contact our customer support at 800-833-1258 Option 2.  Perhaps the email address we have on file is incorrect. 

  What do all the columns on my report mean? 
    We have several report formats.  But this describes our most common report.  Open this Example Report to follow along with the numbers below.

1.  Lab Sample ID:  Every sample that arrives at AT Labs is assigned a unique number. 

2.  Lab Code:  This indicates which AT Lab performed the analysis.  ATOH - Our lab in Boardman, OH.  ATCA - Our lab in Livermore, CA.

3.  Date Sampled:  The date the sampling started.  This information is provided by the customer.  If no date is provided, this field will be blank.

4.  Client Sample ID:  This is the identifier provided by the customer, if any.

5.  Media:  Media that was tested.  For our Trace Air monitors, 521A - Means one cover removed during sampling.    521B - Means two covers removed during  sampling.

6.  Media Lot/Serial Number:  Primarily used for AT badge lot and serial numbers.  Each badge receives a unique serial number when manufactured.

7.  Analytes Requested:  The chemicals tested.  Keep in mind there are sometimes multiple names for the same chemical.

8.  Quantity Found

  • Total: Amount of Chemical Detected on the sampling media (badge). This intermediate number does not take into account the Sampling Time/Volume. This number is NOT to be compared to any regulatory limits.
  • RL:  (Reporting Limit) This is the lowest amount of the chemical that can be reliably measured to be on the sampling media.  This is NOT a regulatory limit.  This is a limit of the analytical method. 
  • Units:  This is the reporting unit of the quantity found.  It is almost always "UG", micrograms. 
  • 9.  Sample

  • Vol (L): Volume of air collected during sampling. Sampling Volume (L) = Sampling Rate (L/min) X Sampling Time (min). For diffusive monitors, the sampling rate varies depending on the design of the badge and the size of the molecule.  Need a sampling rate?
  • Time (minutes): The amount of time the media was exposed to the air. This number is supplied by the customer.  If the customer only reports the sample volume on their COC, this number will be blank.
  • 10. Concentration:

  • This section used to be called Concentration/Exposure.  To allow for larger font, we use the more generic "Concentration" title.  If there are no values here, the sampling time/volume was probably not provided on your paperwork.  If you have this information, contact us and we will send a revised report.
  • Found:  This is the concentration of the chemical.  This is the number to compare against a regulatory limit.  It is the average concentration for the period time monitored. It is an 8 hour TWA only if the sampling was for 8 hours.
  • RL, (Reporting Limit) This is the lowest level the monitoring system could have reliably measured for the period of time monitored. This is not the regulatory limit.
  • Units, This is the reporting unit of the Found and RL values in the Concentration section is being reported in.  It can change depending on what is applicable for the chemical of interest.  For example, Benzene will be reported in PPM, but Lead will be reported in mg/m3.  When comparing the Found value to regulatory limits, it is important to make sure the units are the same.
  •    Equations used to determine the Exposure:

                                                                Quantity Found (ug) on media

    Exposure (ug/L)            =          ---------------------------------------------------------

                                                    Sampling Rate (L/min) X Sampling Time (min)

     

     

                                                                                          1 mg                      1000 L

    Exposure (mg/m3)         =          Exposure (ug/L) X --------------  X   ------------------

                                                                                       1000 ug                    1 m3

     

                                                                                                  Molar Volume 24.1 (L/mole)

    Exposure (ppm)            =          Exposure (ug/L)  X  --------------------------------------------------

                                                                                          Molecular Weight (g/mole) of Chemical

     

    Assay Technology, Inc. uses the Molar Volume at 22 C because most work places are closer to this temperature. The sampling rate is either the flow of air through an active sampler (cassette, tube) or the sampling rate for a specific chemical on a diffusive sampler.  Need a sampling rate for a diffusive sampler?

    Which column has the data that I am looking for?
    In most cases, it is the FOUND column in the Concentration section. 
    Is the exposure a "TWA?"
    The exposure on our report is the analyte's average concentration in the air for the period of time that was monitored. It is NOT necessarily an 8 hour time-weighted average (TWA). It is an 8 hour TWA only if you monitored for 8 hours.  If you want to convert the exposure to an 8 hour TWA and do not know how, please call for Technical Support at 800-833-1258.  Based on what you know about the environment that was sampled, you will need to decide what happened while you were not monitoring.  For example, if you monitored for 5 hours, then what happened during the other three hours?  Do you expect the exposure rate would not change or did any possible exposure end?
    Is the Concentration Reporting Limit the Regulatory Limit?
    No. The reporting limit is the lowest concentration the analyte would have to be present in order for it to be detected by the analytical method.  It is our goal to have the reporting limit be no more than 1/10th (one-tenth) of the applicable regulatory limit when a customer the monitors for expected time periods.  So, it is very possible for an analyte to be detected, but not be over the regulatory limit.
    Why do the Concentration reporting limits vary on my samples even though I am testing for the same chemical?
    The reporting limit will vary on samples because it is a function of time. The longer the sample time, the larger the sample volume, which increases the sensitivity of the badge, providing a lower reporting limit. Conversely, a shorter sample time will results in a smaller sample volume, and higher reporting limit. 

    For diffusive monitors, the reporting limit for each chemical on the same monitor will vary as well.  Chemicals diffuse into the monitor at different rates.  A big molecule will diffuse slowly.  While a small molecule will diffuse relatively quickly.  So the sampling rate will vary depending on the chemical, which means different sample volumes, which means different reporting limits.

    What is Total Quantity Found (ug)?
    This is an intermediate measurement used in the calculation of the concentration.  It is not to be compared against a regulatory limit.  The quantity it is referring to is the amount of the analyte that was found on the sampling media in micrograms (ug).  Once this number has been determined, the sampling time and sampling rate of the badge are applied to calculate the exposure (ppm).
    What does "ND" mean?
    ND stands for None Detected at or above the reporting limit.  In other words, the concentration was so low that the instrument could not detect it.
    My result is over the regulatory limit. What do I do now?
    It is Assay Technology’s intent to provide smart, effective products and services that people can utilize in their health and safety plan. We are not in a position to be able to manage a company’s safety concerns. However, frequently, customers choose to: monitor the area of concern again, reevaluate their safety equipment (hoods, etc), reevaluate their procedures, and/or hire a safety consultant.
    Why are the Regulatory Limits on the reports?
    Many customers have asked for Regulatory Limits to be added to our reports.  We were hesitant to put them on our reports because it is impossible to put all applicable regulartory limits on a single report template.  In general, if an OSHA limit was available, we have referenced it.  If there was no OSHA Limit, but there was an ACGIH limit, we referenced the ACGIH limit.  If neither OSHA nor ACGIH have a published limit, we have referenced a NIOSH limit.  When there were none available, the section was left blank.  Please read the disclaimer on the report.  Clients should be aware that more stringent international, state, local or organizational exposure limits may supersede the limits included with the report.  Because of this, some customers have asked that we NOT have regulatory limits on their reports.  Clients wanting regulatory limits removed from their reports should contact our customer service department.  It is a simple update to your account.
    My result is so high, I suspect there may have been an error.  What could have gone wrong with the monitoring?
    It is important to thoroughly explore the possibility that there is no error and the concentration reported properly reflects the concentration of the chemical in the air. However, errors certainly are possible. For diffusive monitors (badges), probably the most common error that leads to a very high result is when the badge is splashed with the chemical. Even a tiny droplet can cause a significantly high result. Also, if someone touches the badge while they are working with the chemical of interest, a falsely high result is possible. These errors tend to lead to extremely high results. Other errors, like not handling the monitors as specified by the manufacturer are possible and can also cause results to be biased high.  Certainly it's possible there was something wrong with the sampler itself or with the analysis at the lab.  Obviously we work very hard to make sure this does not happen.  However, we are happy to investigate your concerns when they come up.
    What does the message "Caution: Sample not returned within Manufacturer's Maximum recommended Holding Time" mean?

    Most chemicals are not stable on sampling media indefinitely.  There is a length of time between sampling and analysis where the accuracy of the result might be affected due to chemical breakdown, reverse diffusion, etc.  Based on storage stability data for a particular monitor, samples that arrive back to the lab after the recommended holding time has been exceeded are flagged with a note to use the data with caution.  In many cases, it is not possible to determine exactly how much the results have been affected.  However, a badge that should have been returned within a week, but was stored in a freezer for 2 weeks before it arrived at the lab will be less affected than a badge that was stored for 2 weeks in an unconditioned warehouse in the summer.  Recommended holding times are listed on the technical inserts included with all Assay Technology products.  They are also available online.

    Why does the result say "VOID?"
    When each sample is received, it is checked to see if it is in good condition.  If there is a significant problem and any result that would be obtained from analyzing the sample would be severely compromised, then the lab will not proceed with the analysis.  When this happens, the report will read "VOID" in the quantity found column and no exposure will be given. 

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