We can find direct gas and direct fuel heaters.
Direct fired heater carbon monoxide.
Carbon monoxide poisoning occurs from exposure to these gases in enclosed spaces creating extreme hazards for all tradespeople.
Combustion by products depending on a building s intended use direct fired.
Direct fired heaters cannot be used in a tightly sealed structure unless windows and doors can be opened for air exchange.
Direct fired heaters are both more efficient and less expensive than indirect fired heaters.
Having a thorough understanding of all of the differences between these two heater types will ensure you choose the optimal solution for each project.
Generally direct fired heaters are used on construction sites outdoor applications or warehouses.
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.
Most users run fired heaters with a fuel lean mixture allowing an overabundance of air.
In addition to the combustion adding humidity and carbon monoxide to the environment.
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.
Direct fired heaters applications.
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.
On the contrary indirect heaters provide 100 dry and clean air and can operate in closed spaces.
Adds moisture and carbon monoxide into the air.
Table 1 upper limits for combustion gas emissions from direct fired units and result ing space concentrations 2 3 4.
The heat is transferred directly to the product in process.
A direct fired heater works similary to an oven.
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.
However there are some cases where an indirect fired heater is the better choice.
In either case fuel is wasted and emissions increase.
Direct fired heaters are both more efficient and less expensive than indirect fired heaters.
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.
