Heating - Combined heating and ventilation was adopted aboard the Olympic-class liners in that the ventilating air was heated before it entered the passenger or crew accommodations. For 1st Class staterooms, the outside air was forced by fans over bundles of steam tubes in the boiler casings and then distributed to the various compartments by ducts. The steam-tube bundles were divided into two or three sections so that the amount of heating surface could be varied to suit the temperature of the outside air.

   The objection to this form of heating was its inability to regulate the amount of ventilation within a room independently of the amount of heat furnished. Usually, a person desiring an increased amount of fresh air was unable to obtain it without the temperature of the room rising to an uncomfortable degree. This was overcome by a combination of direct and indirect heating, the incoming cool or cold air merely being tempered by the ventilation system heaters to maintain a temperature of about 65 degrees. This is what was described as the “warm air” on the Plenum method . . . (continued)

   Cowl ventilator heads - Cowl ventilator heads, the appearance of which were described earlier, were readily visible on Titanic's Boat Deck and Poop Deck, with only one being located on the Forecastle Deck. The cowls on the Poop and Forecastle Decks appear to be stand-alones without visible housings or motor attachments. However, only a few of these were truly passive ventilators; in most cases they were connected to fans below decks.

   Cowl heads had handles whereby the direction of the mouth opening could be changed. This was an asset when the ship was stopped and the prevailing airflow was not necessarily from forward. As most cowl vents were employed as uptake ventilators, they functioned most effectively when the cowl head was turned to face away from the prevailing airflow or wind over the deck. For this reason, the cowls fitted to Titanic were most often seen facing aft or at a slight angle to the centerline . . . (continued)

   The Sirocco ventilating fan - For assisting ventilation by mechanical means, Titanic utilized centrifugal fans driven by motors powered by the ship’s electrical plant. The centrifugal fan operated on an entirely different principle from the axial fans that most people are familiar with in the form of table or window fans, also referred to as “propeller fans”. Centrifugal fans, also called radial fans, operate on the principle that air has weight and is therefore affected by centrifugal force. Centrifugal force is that which tends to cause rotating bodies to move outwards or away from the point about which they revolve. A centrifugal fan moves air by means of an impeller, which consists of a central shaft about which are fixed rectangular blades. As the impeller rotates, air is drawn into the fan near the shaft and then outward, and then spun around the housing to the outlet. Unlike an axial fan, a centrifugal fan blows air at right angles to the intake. Centrifugal fans produce more pressure for a given air volume than other types of fans, which made them ideal for ventilation systems like Titanic's where large volumes of air needed to be moved great distances. . . . (continued)

   Stokehold ventilation - Designing a funnel to provide the correct amount of natural draft involves a number of design factors. When coal is burned in a boiler furnace, the hot combustion produces gases termed “flue gases.” Aboard ship, those gases need to be exhausted to the outside air through the ship’s funnels. The flue gases inside the funnels are much hotter than the ambient (outside) air and therefore less dense. That causes the bottom of the vertical column of hot flue gas to have a lower pressure than the pressure at the bottom of a corresponding column of outside air. While hot flue gases will rise by themselves due to thermal buoyancy, the higher pressure outside the furnace is really the driving force that moves the required combustion air into the furnace and also moves the flue gas up and out of the funnel. That movement or flow of combustion air and flue gas is called “natural draft.” On ships like Titanic, the air required for combustion had to first descend an average distance of 90 feet from the stokehold ventilators to reach the furnaces situated along each of the stokeholds below . . . (continued)

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