Some times some Auditors behave like this. Thay do not think the issue in a holistic way. Some how they tend to show their authority and misuse the whole concept. In all our day to day activities we come across many such issues. As Dipil rightly said one has to use the most practical solution.
If sand is hazardous what is alternative? Fire extinguishers? Is using chemical is not hazardous? practically once the fire is extinguished with whatever means the remains are collected and disposed safely.
next time such stupid suggestions are given by the auditor, suggest him to use a bicycle to come to your place instead of car / bike / scooter which polluters air
regards
nandish