Unfortunately, the only immunity you can get for Inhalation AND Contact toxins is with a Chemical Seal, which is only available on Full Body Armor and Hazmat Suit. However, a combination of Respirator and Chemical Protection, you would get defense bonuses. As a GM, I would give the lowest of the two ratings (or just the Chemical Protection rating if the gas mask is used) as bonus to the Toxin Resistance Test.
It is possible to defend, just takes a little more work and effort.