LCS Laboratory Inc., specializes in Industrial Hygiene testing, and after many years of laboratory testing we are confident that it is essential to collect and test laboratory blanks.
The question is how many? and the simple answer is: “at least one”. Without a “field blank” sample, your results are biased, and their quality is compromised. Let’s discuss two different aspects: Compliance aspect and Practical aspect.
Compliance with method requirements.
Very often you need to perform an Indoor Air Quality test to demonstrate for authorities like OSHA (USA) or the Ministry of Labor (Canada). If so, you must follow standard NIOSH, OSHA or EPA methods your from sampling to laboratory analysis. Each and every method has a paragraph, where number of blank samples is specified for a particular test. A few examples for your consideration:
- NIOSH 7400 “Fibers in air” requires “2-10 Blank samples” with every batch of samples
- NIOSH 0500 “Particulates in air” recommends “2-10 Blank samples” to be taken and analyzed for every project
If your report is to be be revised by authorities, it is recommended to take and analyze blank samples. If you choose not to collect a blank sample(s), this may compromise your project, and it becomes “non-compliant” – not because it is wrong, but because the method requirements have been violated.
Practical aspects:
A “Travel blank” sample is a sample that you received from a laboratory, and brought to the area for testing. In this case, you simply opened the sample, closed it and returned back to the lab for analysis with the rest of your samples. A “Travel Blank” is your Quality Control sample. We hope that it comes back uncontaminated, but that is not always the case.
Travel blanks can get contaminated in transit, or in the field with improper handling of the cassette or sampling tube.
If the blank comes back clean, then you know that there has been no accidental contamination of the samples.
If a travel blank has traces of contamination on it, then our laboratory will take it into account and adjust all lab results by subtracting the small interference accumulated in transit (from the contamination detected on a travel blank).
Usually we receive 1 blank per batch for small projects, or 2-3 blanks if sampling took several days and a consultant wants to take into account the possible impact of different blanks on different days.
If you want to learn more about Air Quality testing, please visit our Industrial Hygiene Testing page or Residential Air Quality page. If you want to discuss your project, please email us at your convenience.
