Natural Gas Commerical Construction Heat

Ventilation and Combustion Air for Heat during Construction

Combustion Air

All types of equipment that use combustible fuels such as natural gas or propane require air to function correctly. Oxygen is one corner of the “fire triangle”; the other two being fuel and a source of ignition. All three of these elements must be present for combustion to occur. If any one element is missing or unavailable, nothing will happen.

Therefore, even if a heater is fueled up and ready, and the igniter is operating, there will be no fire if no air is available. However, it is not an “on/off” situation. A heater can still work with reduced amounts of air, but will be inefficient, and possibly hazardous if the combustion process is incomplete. One of the products of incomplete combustion is carbon monoxide, or CO, which is detrimental to humans over a period of time.

Oxygen is continually being used as a heater operates, so the air needs to be constantly replenished. Generally, in a large commercial building under construction, this is not a big problem, as doors and windows are constantly being opened. However, if the heater is in a small room, or is isolated in some way, then additional combustion air may need to be provided. The Ontario Gas Utilization Code specifies amounts of combustion air required under certain conditions. Your gas technician that installs the equipment will determine if additional combustion air is needed.

Ventilation Air

Ventilation air is a separate requirement, and is provided to ensure that people working in the area have enough air to breathe when the heater is in operation. Again, the Ontario Gas Utilization Code specifies levels of ventilation air required, based on the BTU rating of the heating equipment. 

A basic rule of thumb is 1 square inch for each 1000 BTUs. In other words, for a 100,000 BTU salamander, you need an opening of 100 square inches somewhere in the near vicinity. It could be a 10 x 10 inch square vent in a wall, or it could be a 36 inch window held 3 inches open, or a door that is blocked 2 inches open, etc. A grate or screen in the opening reduces the air flow, so, the opening then needs to be larger to accommodate the same amount of air. If using a window or door to provide air to the room, then they must be fixed in the open position so they cannot be shut. A note should be placed on the window or door notifying others that it must remain open to provide ventilation air for the heating equipment.

Signs of lack of adequate air

There are several ways to identify a lack of adequate air to a piece of equipment.

  1. Flame colour – a proper flame should be blue and cone shaped. If the flame is yellow, or is lacking in structure and is “all over the place”, it is likely that there is not enough air for the unit, and incomplete combustion may be occurring.
  2. Excess moisture on windows or walls – a certain amount of moisture is produced during normal combustion. If there is a lot of moisture on the walls, check to ensure that there is adequate ventilation air in the area.
  3. Flu-like symptoms among workers – when people are exposed to low levels of CO, they often exhibit “flu-like symptoms”. These can be headaches, nausea, sore throat, fever, etc. If the workers feel better after leaving the area, or after going outside for a break, it is possible that there is not enough ventilation air in the area, and not enough combustion air to the unit.
  4. Its not warm enough – if the area is colder than it should be, check to see that the flame is of good colour and good shape. Inefficient burning will produce less heat.