The California Safe Drinking Water and Toxic Enforcement Act of 1986 (Proposition 65) requires the State to publish a list of chemicals known to cause cancer or birth defects or other reproductive harm. Under the law, the State of California maintains a list of regulated substances, and if any consumer product contains a listed substance, the product must bear a warning to that effect. Please see:

There are many factors that can determine when an air filter should be changed.  How often the HVAC unit runs, air quality, humidity and other factors can vary greatly from application to application.  For most 1”, 2” and 4” deep panel or pleated style filters, it is usually recommended to change the filter every 2-3 months.  In many commercial and industrial applications static pressure can be monitored and the filters can be changed when they reach their recommended final resistance in inches of water gauge.

Most Glasfloss products have an airflow direction arrow printed on the frame of the filter (poly ring filters state air entry side printed on the filter media).

MERV stands for:  Minimum Efficiency Reporting Value. MERV is part of the ASHRAE 52.2 Test Standard that determines the ability of an air filter to remove particles of a specific size from an air stream. Air filters can have a MERV of 1 to 16; the higher the MERV, the more efficient the filter is at capturing particles.  For more information on MERV, please read: