Anybody experienced the 1991 Mt. Pinatubo eruption?

I was only 5 years old during the 1991 Mt. Pinatubo eruption. I remembered going to school and everybody wore a mask to avoid inhaling the ash from the eruption. Although, I remembered that we wore masks for a while, could anybody tell me how long after June 15, 1991 were people encouraged to wear these masks?