MRK-D-0048 V4
Aeroqual Dust Sentry / AQS User Guide
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reference monitor
, or aren’t confident that you can access a well-run reference monitor, then you should
always rely upon the factory calibration.
Important considerations for field calibration:
Location of monitor: The Aeroqual monitor and the Reference monitor need to be located at
the same site preferably with their inlets within 10m of each other, and must be sampling at
the same height. At reference sites using a monitoring shed, on the rooftop of the shed is
usually the best location.
Monitor set up: Both the Aeroqual monitor and the reference monitor need to be set up in
accordance with the manufacturer’s recommendations, with correctly set flow rates and fresh
filters. If you are using a gravimetric method reference monitor, 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. 1-2
weeks is preferred and no shorter than 48 hrs.
Reference monitor selection: Selection of the right reference monitor is critical for a
successful K factor correction. Ideally, reference monitors should be operated in accordance
with local reference method specification. Monitor methods are listed below, in descending
order of preference:
GRIMM / BAM / TEOM: Are best 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 if PM levels are low
. 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. High-
Volume samplers
Other Non-Reference methods (Optical, Open-Path): Existing instrumentation can be used to
establish variance between Aeroqual and a known monitor. This method can be used to
assess new versus old instrumentation, but is not a calibration to a reference monitor.
Steps to performing 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 monitors 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 monitor alongside your reference monitor. Operate both
monitors together. The longer you collocate the monitors, the better.
Collect the data from both monitors. 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
The goal is to create an excel spreadsheet, with 1 column of reference data, and 1 column of
Aeroqual data, in the averaging period you have selected, for instance 1 hour or 24 hour or
24hr averages for the period of your co location.
NOTE: Your zero check data should be included as a point.