Explosion Safety and PSR

In North America, there are dozens of industrial explosions every year. Many workers are tragically injured or killed. Would you believe, a full quarter of these explosions occurred at food industry facilities, including sugar plants (Canadian industrial explosion figures run at about 10% of those in the U.S.?)

Combustible Dust is not a new hazard. The first documented explosion occurred in an Italian flour mill in 1785. Since it is not a new problem, why do these incidents continue to occur? Lack of awareness is likely a primary reason. Can you identify combustible dust, and do you know which safety precautions prevent potentially devastating explosions? Combustible dust explosions: How do they happen?

Five elements are needed for a Combustible Dust Explosion to Occur:

(1) Combustible Dust
(2) Ignition
(3) Oxygen
(4) Dispersion and concentration of dust particles, and
(5) Confinement of the dust cloud.

Two of these elements: oxygen, and confinement of dust cloud are difficult to control as oxygen is found within the air, and materials are generally processed within confined buildings. The other elements can be controlled through the following methods:

• Regular cleaning and removal of dust
• use of proper electrical equipment
• control of other ignition sources such as open flames and static electricity
• the isolation of hazards
• the installation of proper sprinkling or extinguishing systems.

Identifying and controlling Combustible Dust

Any operation in your facility that creates dust including the transferring of sugar or flour, polishing and grinding, the manufacture of powders, and the handling and processing of solid combustibles such as wood or plastic put your facility at risk.

It doesn’t take much, either. Less than 1 mm (1/32 in.) of dust, covering just 5% of a room’s surface area, constitutes a significant hazard. Controlling dust accumulation is critical to preventing explosions.

Dust Collection System

Use cleaning methods that do not generate dust clouds, such as dust collection systems and filters to collect accumulated dust. In Ontario, a Pre-Start Health and Safety Review or PHSR must be conducted when installing dust collection systems. The purpose of the PHSR is to have an independent, fully licensed and insured Ontario Professional Engineer examine the dust collection system for compliance. If not compliant these systems may not be able to cope with the explosive force and may themselves explode. It is also the Law in Ontario.