ALL Open Bag Filter Units pose an explosion risk which increases with the airflow through the unit.

Therefore the larger units pose a higher risk than smaller units.

 Even the smallest open bag filter units must not be
 situated within 3 metres of operatives, walkways or
 combustible materials unless the filter is protected by
 a suitable screen.

The following are strict HSE guidelines applying to the safe location of open bag filter units:

Open Filter Bag Units with airflow less than 0.5m³/sec = 1,065ft³/min = 1,800m³/hr

• These would quickly disintegrate if the contents were ignited, but would not produce high explosion pressures or widespread effects.

• Fire risks may exist, so if unenclosed do not place them within 3 metres of operatives, combustible materials or walkways.

• Alternatively provide a suitable baffle or deflector plate made of non combustible material to direct flames or burning material to  a safe place.

Open Filter Bag Units with airflow between 0.5m³/sec and
2.5m³/sec  = 1,065ft³/min to 5,325ft³/min = 1,800m³/hr to and 9,000m³/hr

• These would not be expected to develop high explosion pressures but the effects of discharged flame and burning material would be proportionately greater.

• Where such collectors must remain within the workroom provide one of the following precautions:

1. Total enclosure within a strong metal cabinet provided with either an air outlet large enough in area to act as explosion relief or explosion vents. 
   Outlets or vents should preferably discharge to a safe place outside the workroom or, if inside, discharge at least above head height.

2. A baffle or deflector plate made of non combustible material to direct flames or burning material to  a safe place.

3. Put the collector some distance from operatives, combustible material or walkways. Insufficient research evidence currently exists to judge fireball size, but 10 metres separation is likely to be adequate.

Open Filter Bag Units with airflow greater than 2.5m³/sec = 5,325ft³/min = 9,000m³/hr

• Site these outside or enclose them in a strong cabinet fitted with explosion vents that discharge to a safe place.

P&J can quote to provide a suitable steel baffle, steel enclosure and/or explosion vent/ relief where required, for any of the above.