St 1 dust - Dangerous or not?

Hope all of you readers are doing well. It is the time of Diwali here in India and everywhere one can see people in the festival mood. Be careful and safe & have a wonderful Diwali.

Today I am trying to clear another misconception which I have come across while talking about St 1 dust. Many of our clients have told me that we are handling St 1 dust which is also the so-called "WEAK EXPLOSION" hence the risk is low. 

I always give them the example of Imperial Sugar Explosion in 2008 where a St 1 Sugar dust lead to 14 fatalities or Didion Milling Co. explosion in 2017 where St 1 grain dust was to blame for 5 fatalities, a dozen injuries and $1.8 million fine.

Combustible dusts are ranked into one of four classes i.e. St 0, St 1, St 2 and St 3. The level of explosion violence increases as we go from St 0 to St 3. The only dust that has zero risks of the explosion is a St 0 dust. However, all other dusts have an explosion hazard including the St 1 dust which can compromise containment on a piece of equipment, or blow out the walls of a building. Grains, Sugar, Fluor, etc. all fall in St class 1 dust.

Practices for dust are the same irrespective of what the St class is, including explosion prevention and good housekeeping, explosion protection and isolation. Additionally, the employees need to be trained in the hazards associated with the handling of dusts.

Every company handling combustible dust should have the powder properties available with them. Dust Hazard Assessment (DHA) should be carried out for all dust handling areas. Basis of Safety shall be established for each area and each unit operation such as Explosion Prevention, Avoidance of Ignition Source or Explosion Protection.

Hopefully, after reading this article you can understand whether your powder/ dust is categorized as St 1 or St 3.