To answer your question... Yes, in many cases boosting trimix would contaminate an otherwise oxygen clean system.
Boosting pure O2 requires the entire system wetted components to be what is called 'oxygen clean', so your concerns regarding also using the same system to boost trimix are valid. There are no issues with boosting pure diving grade helium, it's going to be as clean as the oxygen. Helium is often boosted to produce trimix, and you can use the same oxygen booster on pure helium without concern. You can even use an oxygen booster to boost blended trimix, from a mechanical standpoint... but there are concerns regarding boosting trimix contaminated with hydrocarbons.
Boosting the already blended trimix is a different circumstance because trimix is usually made by adding helium and sometimes a little oxygen (or vice versa), and then topping off with ordinary compressed air.
The concern, especially in a remote location, is the quality of the compressed air being used to make the trimix. If the air used to blend the trimix is
not what is generally described as OCA purity, that is to say only the typical dive shop CGA Grade-E quality or of unknown quality (often the case in remote locations and private compressors without quarterly testing), then there is a substantial likely hood the trimix will contaminate the system with hydrocarbon condensate if a sufficient volume of trimix is boosted.
If you are able to determine the trimix was made with compressed air that is what the diving industry describes as OCA grade, then you are OK to proceed with boosting trimix. If not, then you risk contaminating the booster, whips and related components. While you are unlikely to experience a booster fire when boosting trimix, you may experience a booster fire when later boosting oxygen. Oxygen-related fires and explosions can result in serious injury or death. The 'clean state' of equipment applies only prior to initial use. Thereafter, periodic inspection and cleaning are a necessity for any booster.
Nearly all compressed oxygen gas produced in the US is what is known as USP quality, meeting or exceeding United States Pharmacopeia quality ...
www.divegearexpress.com
Pure helium is used in the blending of mixed breathing gases that contain an appropriate amount of oxygen suitable for diving applications. Helium ...
www.divegearexpress.com
www.divegearexpress.com