Why has our community been doing disinfection?

I don't understand why it takes a week to kill pyrethrum. It will take some time for pyrethrum to eliminate its medicinal properties. Once a week may be different, it is used to kill rats, cockroaches and mosquitoes.

If there are only eight six-story buildings and three or four restaurants downstairs, it is not too much. There are restaurants in small places, which are hotbeds of environmental sanitation and pests. The management office did a good job.