Your system looks good. Condensation occurs when temperature decreases, never when temperature increases. The filter holder should also be heated at the same or higher temperature than the inlet or you may experience condensation on the filter if water dropletts are pumped in the inlet tube (in case of fog). In case of fog you will sample dry + wet aerosol and you have to remove water droplets (e.g using an impactor) if you want to sample dry aerosol only. Keep in mind that air temperature decreases when passing through the filter because of depression.

REmi

2 comments/questions:

1. You indicate to heat the filter because of condensation by the fog droplets; but in the same sentence you mention: remove the droplets. In case of fog droplets and unheated filter it will clog

2. Do you have experience with the pressure drop and thus adiabatic temperature drop in polycarbonate filters?

1. My sentence was written to long. If dropletts are removed, dry aerosol is collected and condensation is dramatically reduced. If fog is sampled, dry+wet aerosol is sampled and condensation may occurs.

2. Yes, in a coastal environment (Mace Head, Ireland and Kerguelen Island) but rather with cascade impactor and closed filter holder. I have not noticed issues with open face air filters.

REmi

Axel Berner studied the condensation effect in cascade impactors for the Po-Valley fog experiments and we tried it in the lab at high humidities, but did not find it because the air heat up again at the next stage where compression occurs

Hi Rémi and Harry, thank you for your answers. Harry, in that case, do you suggest heating both, inlet and holder, or not?

Sandra:

I think removing the fog droplets with a pre-cyclone or pre-impactor is more important.

However it also depends on what you want to collect: what  is the size of the particles that you are interested in?

Good morning Harry,

I'm interested in PM10.

I just notice now that you are in a heated room; that means that the sampling line and the filter are at a higher temperature and thus do not need any heating.

Actually, suggestions can better come from the real expert colleagues in this field who run stations on mountain tops:

PSI  Switzerland; Jungrfraujoch

Clermont Ferrand Puy the Dome

Univrsity Vienna high alpne sites

Did you consult their papers?

Thanks Harry,

I have some papers from the Jungfraujoch station and will read them again to see if they can help me. Also had talked to the Vienna group to learn from their experience.

Dear Sandra, the topic is interesting. I wish these documents may support you.

Moreover, I suppose you will have to consider also the effect of humidity on particle (size for instance..).

Cheers, Valerio 

ftp://ftp.wmo.int/Documents/PublicWeb/arep/gaw/gaw153.pdf

 http://www.ecn.nl/docs/library/report/2000/c00061.pdf

Valerio

Apologies but I notice that you attached a report that I wrote: thank you

The first link does not open?!

Hi Harry!

I don't know why there is this problem. I have no difficulties to access the file.

I downloaded and attached it here (WMO/GAW Aerosol Measurement Procedures  Guidelines And Recommendations)

Regards

Valerio

Valerio

went to the WMO site and got it there; your link does not work for me

Thanks Valerio:-)

I'm currently reading all I can find about this problem, before I decide the final setup of my collecting system.