Machine Learning to predict risk of items
This sounds like a homework problem and those are frowned upon on this web site; so I'm going to be cautious about helping you and just give you general guidance:

1 - be very, very careful about picking models before you do anything else. That is a bit of Researcher Bias and you should try to avoid that; let the data tell you where to go, not the other way around. 

2 - you have to think about what "factors" you can use to describe each chair. How old is it? What color is it? Does it have wheels or not? Some of these features will have an effect on your models, others will not. But it should be your goal to start with a long list of factors and then try to model them out and see which ones have an effect on your results. 

Start putting a list of factors together and then you will be in a better position to continue your studies.