Can we use one helmet for everything?
Even the best helmets are not able to protect against every type of impact. For maximum protection they have to be optimized for the type of blow you expect. Some sports have sharp impacts against pavement, which has zero resilience. The energy spike is very sharp and short. Other sports are played on turf or something with a little bit of resilience. That makes an enormous difference in the helmet you need.
Single use helmets are mostly made with expanded polystyrene (EPS) because of the nature of EPS material. It is strong, light, easy to manufacture and has excellent crush characteristics but with very little rebound. It recovers some part of its thickness Once crushed, but does not recover its protection. If you don't discard it after the first hit, you will be in for a nasty surprise if you happen to hit on the same spot for a second hard impact! Bicycle, motorcycle, roller skate and equestrian helmets normally use EPS for impact energy management. Below is the examples:
The multi-use bicycle helmets were made with expanded polypropylene (EPP). EPP looks like EPS, but has a slightly rubbery feel. It recovers slowly after a blow and is good for more hits. Nobody can tell you how many more hits it can sustain but it is more than one time. Its crush and manufacturing characteristics are not quite as good as EPS, so the helmet might have to be thicker. Multi-hit helmets are mostly made with butyl nitrate foam, a "squishy" but dense foam which is good for many impacts. It is mostly black or gray. It is heavier than EPS and cannot manage as much impact energy for a given thickness. Hockey and football helmets are made this way, and so are whitewater, old-style skateboard and aggressive trick skating helmets.
There are many muti-functional helmet on market. As you can easily find that helmet is both applicable in skate and bicycle helmet. The reason behind is that the helmets meet the safety standard for the application of both cycling and staking.
In conclusion, you will have to be very careful to find what you are looking for. Helmet requirements vary for different activities. Although the technology has advanced enough to combine multi and single hit helmets, we suggest that do not use one helmet for multiple sports unless you look carefully. So look carefully at the certification stickers to be sure the helmet is certified for the sport(s) you want to use it for.