MRK-D-0034 V2.0
Aeroqual AQM 65 User Guide
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fresh filters. If you are using a gravimetric method reference instrument, you must follow
appropriate filter conditioning and weighing methods.
Duration of colocation:
As a general rule, longer is better, as this will give you more data
points and therefore more confidence in your field calibration. It’s important that the colocation
is carried out during the same environmental conditions expected during deployment.
Two
weeks is ideal, and no shorter than 72 hrs.
Reference instrument selection:
Selection of the right reference instrument is critical for a
successful K factor correction. Ideally, reference instruments should be operated in accordance
with local reference method specification. Instrument methods are listed below, in descending
order of preference:
BAM / TEOM:
Are ideal as they are continuous methods, meaning more data can be collected
in a shorter period of time, giving a more accurate K-Factor. BAM data can be noisy at hourly
averages, so consider using 24hr averages.
This is Aeroqual’s suggested method, as lots
of data can be collected quickly, with no need for expensive lab work.
Partisol / Low volume samplers (47mm Filter):
Can also be used, however will need to be run
for a longer period of time as they operate on 24hr averages (i.e. 1 data point per 24hrs). Filters
must be appropriately prepared and transported. Lab and field blank filters should also be used.
Balance accuracy for pre and post weighing should be better than ±0.0001 µg.
Other Non-Reference methods (Optical, Open-Path):
Existing instrumentation can be used to
establish variance between Aeroqual and a known instrument. This method can be used to
assess new versus old instrumentation,
but is not a calibration to a reference instrument.
High-Volume samplers:
Not recommended due to documented variance between these and
other methods and potential for filter contamination.
6.3 Steps to perform a K factor correction
Beta Attenuation Monitors (BAM) measure PM loading on a filter tape, using a radioactive source and
a detector. The amount of PM measured is proportional to the amount of beta rays which are blocked
from passing from the source to detector by the PM on the filter tape. TEOMs use a high precision
microbalance with a special filter to calculate PM concentration. BAM and TEOM instruments run
continuously and data is available at as low as 10 minute averages. This data can be noisy, so Aeroqual
recommend that 1 hour or 24hr averages are used to minimise this noise.
Gravimetric methods (Partisol, Low volume samplers using 47mm filters) have some additional steps.
It is critical that correct filter conditioning and pre/post weighing processes are carried out.
Install and commission your Aeroqual instrument alongside your reference instrument. Operate
both instruments together. The longer you collocate the instruments, the better.
Collect the data from both instruments. Using Microsoft Excel or similar, remove any odd
spikes, error, or automated zero calibration data.
(Gravimetric only)
calculate your concentrations using the following equation:
𝑪𝒐𝒏𝒄𝒆𝒏𝒕𝒓𝒂𝒕𝒊𝒐𝒏 =
𝑭𝒊𝒍𝒕𝒆𝒓 𝒘𝒆𝒊𝒈𝒉𝒕 𝒂𝒕 𝒆𝒏𝒅 − 𝒇𝒊𝒍𝒕𝒆𝒓 𝒘𝒆𝒊𝒈𝒉𝒕 𝒂𝒕 𝒔𝒕𝒂𝒓𝒕
𝑻𝒐𝒕𝒂𝒍 𝒗𝒐𝒍𝒖𝒎𝒆 𝒐𝒇 𝒂𝒊𝒓 𝒔𝒂𝒎𝒑𝒍𝒆𝒅
Select an appropriate averaging period, 24hrs is usually appropriate. Calculate your averages
for both reference and Aeroqual using this formula:
𝑨𝒗𝒆𝒓𝒂𝒈𝒆 =
𝑺𝒖𝒎 𝒐𝒇 𝒓𝒆𝒂𝒅𝒊𝒏𝒈𝒔
𝑵𝒖𝒎𝒃𝒆𝒓 𝒐𝒇 𝒓𝒆𝒂𝒅𝒊𝒏𝒈𝒔