Not change last activity with ajax.

[eluser]InterMedio[/eluser]
Hello everybody. Whean I authorized in simple page(without ajax), I automatically logout from 1 hour (so if last actuvuty = 1 hour). If I entered to chat (this is page with ajax using), then my last activity updated evere 2 sec (so with each running ajax), but user can be not active. I need to chat work same as simple pages (without ajax), so with updated ajax not update last activity...
Thanks.