Do lights have to be a specific kind to he hung vertically

[him]

I have some hps lights that i want to hang vertically without a reflector and i think i read somewhere only certain kinds of lights can be hung vertically..is this true? what happens if i just hang them vertically anyways?

 

[OGrower]

some lamps are universal some are not. google your brand or manufacturer to find the specs.
i wouldnt hang them vert if they are not designed to be...

 

[El Cerebro]

They may have a code printed on the glass, U for universal position, can't remember the base-up, base-down, and horz codes but google has them. If no position code with the model #, that means universal too.