Was at work, outside on a smoke break. It was a bright, sunny day, with a solid blue sky with not a cloud in the entire sky and no wind blowing. I first noticed the object because there was nothing else moving above ground level. I was startled to see this thing, because it was a foreign object floating around in a place where foreign objects aren't supposed to be (in the middle of a chemical plant), so that's why I started paying attention to it. Then it fascinated me, because I couldn't figure out what it was or what it was doing, so that's why I kept watching it for the 5 minutes or so until it moved out of sight.
Saw a perfectly round white object about the size of a volleyball ascending at a height of about 10 feet from behind a building approximately 40 feet in front of me. It ascended slowly to a height of about 40-50 feet while traveling due north. It continued traveling due north for a half-mile or so, then stopped and came back due south until it was directly above me, then went straight up until it diminished to pinprick size and finally disappeared completely.
I first perceived the object as being circular (flat). But it never seemed to change shape regardless of my perspective of it, so I later changed my perception from circular to spherical. In retrospect, it seemed to have been a round ball of light, which never changed color or brightness in the entire time I watched it.
My reactions during the sighting were to move a short distance away from my original vantage point to get a clear view of its movement, look around for any people to witness it with me, and just be shocked at what I was seeing. A couple of people finally came by after it was ascending straight up, and I pointed it out to them. They both said it was probably either a satellite or a weather balloon and didn't think anything about it. After it disappeared, I went inside and told my boss and a coworker what I had seen. Then I went to the guard-shack to see if their video cameras had by any chance captured any of this. Unfortunately, it hadn't been pointed in the right direction. I mentioned it to a couple of other coworkers over the next few days, mainly hoping to hear that one of them might have seen it as well, but none of them had.
That night, I emailed my family & told them about it. I also looked for a website to report it. I wasn't aware of Mufon at the time, so reported it to some other site. No clue which one it was, and never had any response from them. I actually regretted doing that later, because I figured it put me on some list of crazy people that need to be monitored.
Just looked back at the emails to my family to come up with the exact date before typing this, so I see it's been 2-1/2 years since this happened. And it's still bothering me, because I have no idea what it was, and I think about it frequently. I used to think all those people seeing UFOs were crazy, now I'm mad that I can't get an explanation for what I saw with my own two eyes.