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9.32.3.4.(7)
OH1OS3
ObjectiveOH1 Indoor Conditions
Attribution
Application
Application 1: 
Connection of outdoor air supply ducts that are:
  • installed between the furnace and the outdoors, and
  • not connected to an outdoor air supply fan.
This applies to outdoor air supply ducts in self-contained heating-season mechanical ventilation systems coupled to forced air heating systems serving single dwelling units with 5 or fewer bedrooms that are supplied with electrical power and a heating system, in buildings to which:
  • Part 9 applies [see Sentence 1.3.3.3.(1) of Division A for application of Part 9], or
  • Part 6 applies [see Sentence 1.3.3.2.(1) of Division A for application of Part 6 and Sentence 6.2.2.1.(3)].
Exceptions: 
except as stated in Sentence 9.32.3.1.(1), which applies to heating-season mechanical ventilation systems designed to comply with CAN/CSA-F326-M.
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Intent
Intent 1: 
To limit the probability that the full negative pressure in the return air plenum will not be available to draw in outdoor air, which could lead to the inadequate replacement of indoor air with outdoor air.
This is to limit the probability of the inadequate control of:
  • airborne pollutants,
  • oxygen and other components necessary for breathable air, or
  • relative humidity, which could lead to condensation, which could lead to the generation of pollutants from biological growth or from materials that become unstable on wetting.
This is to limit the probability of negative effects on the air quality of indoor spaces, which could lead to harm to persons.
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