Seleing heavy gas for instrument diplay purge

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The discussion focuses on selecting a suitable gas for purging an outdoor display unit that operates in varying temperatures. While purging air is not mandatory, it is considered beneficial to prevent condensation and oxidation. Options discussed include R134a, argon, and CO2, with concerns about moisture absorption and the weight of the gases. Nitrogen is mentioned as a common purging gas, but its lighter-than-air property may not suit the gravity fill requirement. The goal is to ensure a dry gas fill to maintain display quality in humid conditions.
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We are working on an outdoor display unit. It will operate at a wide range of temps. There is not a requirement to purge air from the encasement but would be a smart decision I think. my thought was to use a gas that is very dry and heavy enough to simply purge the air and sit in the device like water while the sealed lens is installed.

These are being made in small qtys and volume is less than 1in3 each. Thought was to use R134a since it is a very heavy gas but wondering if that is really an overkill for this. Argon might work just as well and we have both in the shop. Not sure if either will readily absorb moisture from the air for the few minutes they would be sitting until sealed. A cheap and easy solution might be CO2.
 
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What's the purpose of the purge? If you're looking to dispell oxygen to prevent oxidation of anything inside, I've seen nitrogen most commonly used.
 
Condensation in certain cold weather conditions is our primary concern. It would not affect our circuits at all but does not project an image of quality. N is lighter than air so that would not fit our gravity fill considerations here. We are in a fairly humid climate several months out of the year so have a dry gas fill would hopefully be a quick easy step to ensure a quality display in cold temps.
 
You could always do the assembly in a low humidity room (environmentally controlled, RH & Temp, walk-in chamber).
 

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