When drilling with oil based mud (70-80C) one often have oil vapour concentrations of at least 300% above acceptable level and oil fog of at least 3000% above acceptable level in the worker breathing zone in the working area in front of and between the shakers.
An advanced exhaust hood (Patent pending) which keeps the emissions within the border of the shale shaker screen, together with a well designed replacement air system with continuous flushing of the operators working area. The combined effort results in an excellent working environment well within the authority's requirements.
Olesen Consult HVAC AS, have developed and till now installed and tested this type of system at. See "Project/ Reference". Video & Picture

Statfjord A - Conditions

Before mg/m3 air

After mg/m3 air

NPD req. mg/m3 /8timer (12timer)

Oil fog

1,4 - 21,1

< 0,1

1,0 (0,66)

Oil vapour hydrocarbons

1 - 122

0,1 - 0,4

50,0 (33,3)

The important issue in a push & pull system is the interaction between the properly designed supply system which continually flush the operators working area with clean air and the innovative exhaust hood (which prevent polluted air from entering the working area) with a dynamic separator draining the liquid back to the shaker screen, before the air is blown out through a high velocity stack (high velocity to have minimum settling in the ducts). 

A system have an inlet water separator removing 95% of water particles above 30 my, silencer, steam/electrical) heater, supply axial fan, silencer and duct system connected to the inlets. The exhaust system have AISI316L exhaust hoods, (here at the smoke test) duct system, silencer, exhaust axial fan, silencer and a vertical non return outlet. 

At existing plants with 4 shakers the motor at the supply fan are in the range of 20 - 30 kW and the exhaust fan motor 40 - 50 kW. The heater raise the temperature to +10C, which is sufficient. We always utilise as much as possible of the existing installation with regards to mechanical & electrical & instrument systems. 

When this method is applied to all areas with open handling of the drilling mud, there will be no conflicts with the requirements of the working environment. This apply to all types of mud. 
This is the only known documented ventilation solution which fulfil the functional requirements in force for the working environment in the shale shaker areas from the Norwegian Petroleum Directorate. This system can too be used in other areas with large pollution's like the Hopper-mixing table.
Statfjord A was delivered as a project package incl. Commissioning. At Sleipner A was delivered as a complete installation all inclusive (5 shaker, just exhaust system & 1,5 million NOK). At Maersk Jutlander (4 shakers & 2 million NOK total), delivered at all material and some installation assistance and commission. At Maersk Gaurdian delivering a complete installation all inclusive (4 shaker & 2,5 million NOK), expected finalised week 45/46 - 1997.
Normal project duration 3 - 4 months, with an offshore installation time of approximately 2 weeks.
At Maersk Guardian the oil company paid 2/3 of the costs and saved this at the first drilled hole because of the lower cost of the oil based mud (40$ versus 200$ for the low emission type).
You can see our videos from the smoketests at any of the above mentioned projects, just contact us.