Direct fired heaters cannot be used in a tightly sealed structure unless windows and doors can be opened for air exchange.
Direct fired heater carbon monoxide.
The products of combustion carbon dioxide co 2 carbon monoxide co nitrogen dioxide no 2 aliphatic aldehydes and water vapor are discharged into the makeup air stream and supplied to the building or process.
However there are some cases where an indirect fired heater is the better choice.
Adds moisture and carbon monoxide into the air.
Proper ventilation is required to avoid buildup of gases such as carbon monoxide.
Figures 1 and 2 show diagrams of non recirculating direct gas fired ahus and figure 3 illustrates a recirculating direct gas.
However there are some cases where an indirect fired heater is the better choice.
Table 1 upper limits for combustion gas emissions from direct fired units and result ing space concentrations 2 3 4.
Most users run fired heaters with a fuel lean mixture allowing an overabundance of air.
Indirect fired heaters do not produce carbon monoxide carbon dioxide or nitrogen dioxide so they are safe to use in tight spaces although they still need an exhaust outlet.
In either case fuel is wasted and emissions increase.
Direct fired heaters applications.
The heat is transferred directly to the product in process.
A direct fired heating system is typically a device that uses the lower heating value of the fuel to heat the air photos 1 and 2 examples of horizontal rooftop and vertical ground mounted direct fired units.
Carbon monoxide poisoning occurs from exposure to these gases in enclosed spaces creating extreme hazards for all tradespeople.
A direct fired heater works similary to an oven.
Generally direct fired heaters are used on construction sites outdoor applications or warehouses.
These fumes are generated from a variety of sources including direct fired open flame salamander type heaters and other equipment operating within the building envelope.
In addition to the combustion adding humidity and carbon monoxide to the environment.
Having a thorough understanding of all of the differences between these two heater types will ensure you choose the optimal solution for each project.
As a result carbon monoxide and hydrogen go to atmosphere or worse mix with tramp air outside the combustion chamber and burn where it is not desirable.
In addition since the air is emissions free operators can use duct systems to transfer warm air from an indirect fired unit to other nearby spaces.
Direct fired heaters are both more efficient and less expensive than indirect fired heaters.
Combustion by products depending on a building s intended use direct fired.
