| 31. | Door shafts may double as ventilation shafts to reduce the digging, although this is inadvisable.
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| 32. | White ducts are ventilation shafts for the underground areas.
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| 33. | Challis escapes through a ventilation shaft and rescues Ellie.
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| 34. | There were the " disinfectors " who poured the Zyklon-B crystals into the ventilation shafts.
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| 35. | It was therefore decided to sink a new ventilation shaft and work commenced in April 1913.
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| 36. | Their ventilation shafts were covered by metal ventilation louvers, coupled with spark arrestors and dust deflectors.
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| 37. | From 1871 steam tugs were used to pull boats through, and extra ventilation shafts were installed.
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| 38. | In many places the structure was designed to have ventilation shafts to allow some convection inside.
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| 39. | The group infiltrates the quarry and inserts JR into the ventilation shaft above the gold room.
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| 40. | Two ventilation shafts were provided to the tunnel.
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