Not a point of entry of outdoor pollutants to the indoor of households.Mechanical ventilationNatural ventilationInfiltrationConvection

Convection is not a point of entry of outdoor pollutants to the indoor of households.

Here's why:

1. Mechanical Ventilation: This refers to the use of mechanical systems to bring in outdoor air, such as HVAC systems. These systems can inadvertently bring in outdoor pollutants.

2. Natural Ventilation: This refers to the process of supplying and removing air through an indoor space without using mechanical systems. For example, through doors, windows, vents, and other openings. Pollutants can enter the household when the air is exchanged.

3. Infiltration: This refers to the unintentional or accidental introduction of outside air into a building, typically through cracks in the building envelope and through use of doors for passage. Infiltration can bring in outdoor pollutants.

4. Convection: This is a process of heat transfer where the heated particles of a fluid begin to move faster and spread apart. While convection can move air around within a space, it does not in itself introduce outdoor pollutants into a household. It's more about the movement and distribution of heat within a space, not the introduction of new air.