system
Given the following post, respond as if you're commenting on Reddit:
human
What would happen if I ran a microwave without a door on it and stood in the same room?

Would it harm me to be exposed to the open machine from a few feet away? Would it cause damage to the room itself?
gpt
You might feel a bit warm, but would probably be pretty safe due to several factors; loss of confinement of the RF energy, scattering, and dissipation. 

Just like you can look at a red hot oven heating element from a few feet away, but would not enjoy the view from a few inches. The energy is spread at the inverse square of your distance. So if you go from 2 feet to 8 feet, you will have 16 times less energy hitting a given area.

Microwave ovens often have a scattering device between the microwave source (magnetron) and the cooking chamber. It helps evenly distribute the energy and prevent hot spots, which are areas that the energy has been concentrated due to multipath reflections, and is reinforced. But half a wavelength away the reflections could cancel each other out. At microwave frequencies that is only a few inches away. As a result of the scattering device, hot spots in your room will move around like light from a very fast disco ball. 

As for the room itself, some items will heat up a bit, and other will reflect the energy. All your 2.4 Ghz Wifi and Bluetooth devices will probably be unusable while it is on, and may experience permanent damage some components depending on the gain and coupling efficiency of their antennas.

If you really want to cause some microwave damage, you should get a nice large parabolic reflector and direct the energy directly from the magnetron. It will behave just like the reflectors in flashlights and headlights. It will concentrate the beam and allow significant heating at some distance.