GRIMM
Aerosol Technik
Dehumidification methods
from GRIMM
by Eng. Wolfgang Brunnhuber
general information

Moisture / humidity is the greatest problem when
measuring particles in ambient air.

Most instruments on the market heat the probe up to
about 35-40°C to handle this problem. But at the
same time they loose the semi volatile compounds
(SVC).

We at GRIMM have decided to dry the probe instead
of heating to keep the SVC. We begin to dry when
humidity gets higher than 65%.
Silica GEL Dryer
Nafion Dryer
EDM165 & EDM265
EDM165 main parts
Sample Pipe
Humidity
Temperature
Sensor
Dryer
Monitor
Reserve
F ei dl housnig 1 1. 65
DEHUMIDIFICATION
EDM165
Operating Principle
1 1. 07
Silica GEL Dryer
Nafion Dryer
EDM180, EDM365 & EDM565
Benefits of Nafion
Nafion transfers moisture quickly
Water transfers through Nafion as a first order kinetic
reaction.
Water transport is driven by partial vapor pressure
differential.
Nafion transfers water selectively
Water associates readily with sulfonic acid groups and
permeates through the membrane wall.
Nafion needs no maintenance
By the working principle of the Nafion it has the big
advantage that it doesn’t need any cleaning and has a long life time
(if used under normal ambient air conditions over 10years) without
loss of performance.
No loss of semi volatile compounds
Dryer flow schematic
Model 180 Vacuumflow schematic
from
Sample Out
sample pipe
holder
sample pipe
sample pipe
holder
under-pressure
regulator
-550mbar
1.2l/min
from
room
Sample
Head
1.8l/min
CQ
vacuum
filter
Linear
Silencer
Pump
permapure
dryer
CQ
Needle-valve
1
Vakuum
meter
3
Switch
-400mbar
to meassurment chamber
protection
filter for
vacuum pump
Outlet
back
side
Jorge Anjos
Sampling pipe with Nafion tube
RAW Data – 15min average values
RAW Data – comparison to reference daily
values