Wondering what is the heart rate for doing labor work as in weeding the yard for a couple hours and is it dangerous if it's over 100 in the long run?

Heart rate at age 28: Your maximal predicated HR based on your age is 192 +/-10. If you're otherwise healthy, you can exercise to this number safely but you will get tired quickly as you approach it and will need to stop. 80% of your MPHR is 154. You should be able to exercise at this level for long periods of time. A HR of 100 is harmless - you could tolerate that forever.