There's no single official number for pet dander the way there is for wildfire smoke, but HVAC manufacturers are consistent on the range: MERV 11 as a minimum step-up, MERV 13 for stronger allergy/asthma relief. Trane's own consumer guidance puts it plainly — "if you have pets, a MERV 11 filter is a better option than a MERV 8" — and recommends MERV 13 for households managing allergies or respiratory sensitivity.

Where MERV 8 falls short: MERV 8 (the common household default) catches larger particles like dust and lint well, but pet dander and dust-mite debris are fine enough that a meaningful share slips through. Stepping up to MERV 11 catches noticeably more of it.

The certification signal: 3M's "asthma & allergy friendly"-certified Filtrete line, tested against cat allergens, dust mite allergens, and pollen, starts at MPR 1000 (about MERV 11) and runs up through MPR 2500 (about MERV 14) — a rough industry confirmation that MERV 11 is the practical floor for allergen-focused filtration, with 12–13 as the stronger tier.