AT Lab Report - Frequently Asked Questions

Did not see your question?  Call us at 800-833-1258 ext 2 or email

  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 AIHA-LAP, 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 ( 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  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. 

  Why doesn't my report tell me if I passed or failed?

Most commonly, a customer will use our badges to monitor a person performing a regular work task for a STEL (15 minutes) or PEL (8 hours).  Then they will compare the result to an published OSHA limit.  If this was all customers did and there were OSHA STELs and PELs for all chemicals, we would be able to set up a reporting mechanism that would flag the result as a 'pass' or 'fail'.  However, this is not the case.  Customers perform all kinds of different monitoring and use regulatory limits from several different agencies while evaluating their results.  There is too much variety to set up a pass/fail system that would be acceptable for all our customers.

 If you need assistance interpreting your report, feel free to contact us.  We will point to the Concentration Found column and if applicable, the available regulatory limits.  However, keep in mind, we are not a trained safety officer performing evaluations on your site and can not make safety decisions for you.  If you need the services of a certified industrial hygienist, we have many as our customers and can probably find some that are local to you.

  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.
  • RptLmt:  (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.
  • RptLmt, (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 24.45 (L/mole)

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

                                                                                          Molecular Weight (g/mole) of Chemical


    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. 
    I included a field blank with my samples and the result was over the reporting limit.  What does this mean and what do I do?
    Field blanks are used to evaluate any background collected on the sampling media during storage, handling and shipping.  Reports provided by AT Labs will be Lab Blank corrected, but not Field Blank corrected.  If you want your report to be field blank corrected, include a note on the Lab Request Form or contact our customer service department.  This can be done before or after the report as been completed.  For some chemicals, it is common to find low level values in field blanks and is not cause for alarm.  These include formaldehyde, ozone, acrolein, and nitrous oxide.   In most cases, the background found of the blanks are insignificant to the sample results and/or regulatory limit and can be noted, but not used.  There can be cases where field blank results are 5 to 10 times above the reporting limit and can be cause for inquiry.  Problems might include sample mislabeling in the field or the lab and severe sample cross contamination due to high exposures.  Dr. Charles Manning, PhD, CIH, Assay Technology's Technical Director authored a document on the subject of field blanks:  Blank Correction Of Air Samplers