worried about excess heat

Hi Guys, i have just germinated my lowryder2 seeds and about 2 put them under my 400w hps, HOWEVER, i am a little worried about the heat the lamp lets off. I am closet growing and the only thing i have to cool it down is a fan, will this do.????
considering the lamp will be on 18/6 i am paranoid i am going to set the house on fire.

you will have to use your hand as a guide get a thermometer also if your growing lowryder iwouldnt turn the light out at all 24/7 faster bigger grow
they dont need a dark cycle

What kind of fan, oscillating? A oscillating fan will just blow the hot air around. You need an exhaust fan to remove the hot air, and you will also need some type of intake weather you go active or passive it's up to you.

Thanks guys, now i am confused, other guys on here state 18/6 for lowryder??? nevermind.
when i do get them under the light, how far apart will i put the light.?????

a 400 watt will cover a4by 4 area you will need to let your hand be your judge start at about 18 inches no marijuana plants need a night cycle photosynthesis goes on 24/7
with light

ok cheers ganjaman13, thanks for the info, much appreciated.