How to interpret the footnotes on reports
As manufacturer of our own badges, it is necessary to establish guidelines for the use of our badges to better ensure customers will receive quality, meaningful data. Among these guidelines we have recommendations for:
- Storage conditions before and after use
- Holding times: the time between sampling and receipt at the lab for analysis
- Shipping policies.
When badges are sent back to us for analysis and the guidelines are not followed, we automatically note the non-conformance in a recommendation on the report. Customers will frequently contact us about a footnote and ask how the results were affected and whether the data can be used. The answer is: it depends on the circumstances, but we can make educated conclusions on whether the results are more likely unaffected, more likely biased high, or more likely biased low. Here are a few examples:
- A customer used a 566 badge to sample for xylenes, then put the badge in the freezer for a 2 month period. The badge arrives a week later. The result was footnoted as received past the holding time. But were the results affected? Answer: There could be a high bias because there was a lot of time between sampling and analysis. It is unlikely the results are biased low. Xylenes are very stable at room temperature and storing a badge in the freezer makes it even more stable.
- After sampling, a customer leaves a 575 Nitrous Oxide badge a room with the source of Nitrous Oxide still present. Could the results be affected? Yes, even after a few hours, the results are likely biased high. Even with the badge closed, nitrous oxide is probably sneaking through that cap. That’s why we give you the extra protection of an outer sample container (or, as of Spring 2020, an additional lid seal) with the 575 badges.
- A customer does not use a 566 badge until after the expiration date, will the data be accurate? Answer: It is hard to imagine charcoal not working. So, a low bias is very unlikely. However, it is possible the chemical you are monitoring for has collected onto the badges while in storage for that long. So, send in a field bank so the result can be field blank corrected. See below.
Customers come up with many different irregularities. No matter how many studies you perform under different circumstances, a customer will come up with a new environment to ask about. So, when presented with a badge that wasn’t used as directed, we have to make our best judgment as to how the results are affected.
Here are a couple of suggestions you can follow so you don’t have to rely on a best guess:
- Always include a field blank. If you find some background, then field blank correct your results. Or, have us do the correction, based on the field blank results.
- If you are worried about the effectiveness of the badge, send in another blank for us to evaluate (perform a spike and recovery).
By all means, contact us with questions. Since we both analyze and make the badges, we are experts in both. We’re here to help.