請問甚麼是微波盧的熱風對流煮食？

I don't think it is related to microwave oven (微波爐). It is the heating mechansim used in Halogen Pot (光波爐).

In an Halogen Pot, infrared (紅內線) is produced from halogen tubes (卥素管)and the air inside the pot is heated up rapidly. This sets up a strong convection (對流) to heat up the food.

For details in the operation of Halogen Pot. You may refer to the following web-page (written in Chinese). Just read the answer to Q2.

http://lmkbiz.blogspot.hk/2012/07/blog-post.html

As the heating mechanism of Halogen Pot is no different from that of an ordinary oven, surely there is no harmful effect to health.