Standard 1-inch commercial filters need replacement every 30–60 days in occupied buildings. Higher-efficiency deeper filters may last 60–90 days. Buildings with high dust, heavy occupancy, or nearby construction need more frequent changes. Monitor pressure drop across filters if your system has a differential pressure gauge.

ASHRAE 62.1 recommends minimum MERV-8 for commercial occupancies. Healthcare and schools typically require MERV-13 or higher. Verify that your air handling unit's fan can handle the added resistance before upgrading to higher MERV filters.

Clogged filters restrict airflow, increasing energy consumption and reducing heating/cooling capacity. Severely restricted filters can cause coil icing in summer and heat exchanger overheating in winter. Bypassed or collapsed filters allow dust to accumulate on coils, drastically reducing efficiency.

Higher MERV filters increase pressure drop, reducing airflow. This can be acceptable if your fan has adequate capacity, but problematic in older systems. Consult your HVAC contractor before upgrading MERV rating to verify compatibility and adequate airflow.

MERV is the standardized ASHRAE rating used by commercial HVAC professionals. FPR and MPR are proprietary residential-market ratings from specific manufacturers. For commercial buildings, always specify filters by MERV rating for accurate cross-manufacturer comparison.

For commercial buildings, disposable media filters are almost universally recommended. They provide consistent performance and are replaced on schedule. Washable filters require proper cleaning and drying — improperly dried filters promote mould growth.

Ontario's HVAC systems run year-round in heating and cooling modes. Spring and fall transitions — when outdoor air dampers open wider and seasonal allergens are elevated — often require more frequent filter changes. Year-round monitoring is important.

Responsibility depends on the lease. In many Ontario commercial leases, filter replacement in tenant-demised spaces is the tenant's responsibility. Building-wide or common area HVAC equipment is typically the landlord's responsibility. Confirm responsibilities in writing before occupancy.