CURL and process not finishing

I am using CURL to check pages outside my site on the internet for some text, then I email someone on my database who supposedly looks after the site. The script creates a process that does not terminate. It is running on a scheduled cronjob so eventually my site has over the maximum of 20 processes running and it goes offline. It may be that some of the pages I check are hard to get a response from, as CURL tries to return the target URL. I have removed any emailing that it does and still get the problem. Is there any way to check that a process is not terminating after a reasonable time? John