Storage conditions are also a key factor in the shelf life. In the United States, according to 29 CFR 1910.134, OSHA requires that respirators be stored in their original packaging and away from contaminated areas, dust, sunlight, extreme temperatures, excessive humidity, and hazardous chemicals. Canadian CSA Standard Z94.4 has similar requirements.
You should take the following steps for proper storage:
Always keep the respirator in its original packaging
Keep the respirator away from contaminated areas, dust, sunlight, extreme temperatures, excessive moisture and harmful chemicals
Implement good inventory management practices, including inventory turnover.