<<Disclaimer: Verify this information before applying it to your situation.>> I just spoke with Celestial Seasonings at their consumer info. line 800 351-8175 I was told that their bags are heat-sealed. The bags themselves are GF. However, not all of their teas and tea blends are GF - some have barley, etc. so check ingredients on the box before buying. Their equipment is thoroughly cleaned, with no residue, between runs of different types of teas/tea blends, due to their Kosher certification. Vicki