I am trying to create a modular clean room with high humidity/temp, air flow and positive pressure in the clean space.

I have worked out everything but a humidity source.

my options are:

warm mist humidifier with UV filter.
Concerns in design: Is it safe to run a consumer humidifier in an enclosed clean space? If yes, will the positive pressure pose a problem in having additional holes (besides 2 for filtered ventilation) in structure for warm mist from an external source.

or

modify an aquarium heater, suspend in a jar of evaporative water, place in clean space (perhaps with timer).
Concerns in in design: Keeping container of evaporative water sterile through fillings. Any recommendations? What if any chemicals will stop bacterial growth and not be dangerous when evaporated?

Any input would be great. 

Usually humidity control is done back on the air handler recirc system but it sounds as if you are using a total loss system.

There are some very good small commercial humidity systems on the market and as long as it is sized properly there should be no problem with pressure loss, but then again it depends what you means by High humidity.  You may need to talk to an HVAC expert and do some calculations relating to air temp, water vapour, room volume and flow.

Bacteria should not be a problem as long as any condensate on the humidifier is controlled. ( Dont leave it to puddle up ! ) 

Regards,
Dick Gibbons (committee member of the BSI LB I 30 in the UK and convenes 14644 part 8 and 10 for Chemical contamination)