Infrared radiation is invisible to humans and is only detected in the form of heat.
As far as I know, unlike UV radiation, IR is only rarely harmful to the eyes. Prolonged exposure over many years can accelerate cataract formation (mostly with people who work with hot materials such as molten glass or steel). However, IR has a short range. To be sure, if you get close enough to the source with your eyes, you would feel the heat which would cause you to close your eyes or move away long before it can cause any harm. If you suffer from dry eyes, the heater may exacerbate this condition.
Overall, if you keep at a reasonable distance, you should be safe.
Hope this helps.