Guardian Stainless Steel Mug vs Stainless Steel Mug: which is safer?
Thermos Guardian Stainless Steel Mug is our pick: better on PFAS and on the overall hazard picture.
Our pick
Thermos
Guardian Stainless Steel Mug
PFAS grade
A 95/100
Overall grade
A 91/100
Verdict
Buy
Hazard flags
⚑ 1
Material
Stainless steel (uncoated)
Confidence
85%
PossibleBacterial growth in storage
Thermos
Stainless Steel Mug
PFAS grade
A 95/100
Overall grade
B 87/100
Verdict
Buy
Hazard flags
⚑ 2
Material
stainless steel, no stated coating
Confidence
85%
PossibleSeam or lid leachables
PossibleBacterial growth in valve/seal areas
Both products run through the same public rubric: materials, coatings, brand disclosure, lab findings, and recalls, plus a beyond-PFAS hazard analysis. Grades are model-based estimates, not lab tests. How grades work →
More insulated travel mugs: see the full ranking