First of all, it is important to ensure you about the stability of the doorway pull-up bars. The best way to do so is by explaining the safety method on every type of pull up bar.
The leverage doorway bar, for instance, works by forming a rectangular with the door frame. The two edges on the imaginative rectangular are pushing towards the door frame; therefore they are keeping the bar in place even though your weight pulls it down. The top of the bar pushes it against the wall and the bottom part pivots and pushes against the other side of the door frame. As long as these two attachments are good, the bar will safely hold your weight.
The telescoping pull up bars on the other side, are placed parallel on the required height. After this, they are being wedged by expanding the bar. The bar expands to that amount, that there is so much friction between the ends of the bar and the frame door sides, that it is impossible for it to move. However, if you don’t feel safe, or if you have had a bad experience with a telescopic pull-up bar, there are always safety caps to the rescue.