Should I buy this (gently) used, 15 year old, helmet?

It's worthless.

The many issues you cite would be reason enough to trash a 5 minute old helmet.

Many manufacturers also put expiration dates on their helmets, claiming the foam gets too hard or soft or some such and it can't do its job. While that very well might just be a cash grab, it might not be, and so that coupled with the fact that it isn't in pristine conditions means you should not trust it whatsoever.

No. It is safety gear – buy a new one.

The old helmet might make a good pot for a hanging plant but it is more likely to fail dramatically in your moment of need.

The straps would probably come right with a soak in water, but the polystychrene is the functional part and it has failed with age.

It might fill a legal requirement if your location mandates helmet wearing, but it probably won't provide sufficient protection.

The problems you describe absolutely disqualify it from being used (as a bike helmet).

I would not use a 15 year old helmet in any case, even if it did not exhibit any evidence of damage.

Helmets have advanced a lot in the last 15 years. Safety reasons aside from the helmet falling apart (which is more than enough reason not to buy it) modern helmets are night and day more comfortable to wear.

Not worth it.

• Bike helmets are a one-use item- the foam crushes to absorb the impact, and then is useless after.
• Because of this, most helmet manufacturers recommend replacing helmets once ever 3 years, due to a combination of crushing from day-to-day usage (all those times you crammed it into a backpack or had it slightly bounce off a wall while walking with it), and from the foam breaking down on it's own (some airborne solvents, say from cleaning fluids or car batteries) will actually cause helmets to degrade).

I used to ride a motorcycle, and because of the one-and-done nature of helmets, many riders were so strict as to say if you dropped your helmet once from a table to a concrete floor, it should be replaced. Their argument was basically that your brain is important, and worth protecting.

The helmet you've been offered sounds like it's in terrible condition. Frankly, any fifteen-year-old helmet has probably degraded far enough that it's not going to protect you properly, but this one is clear junk. It's not "gently used": it's wrecked.

However, it's condition is largely irrelevant. Don't buy any second-hand helmet. It's as simple as that. A helmet that's been in any kind of significant impact needs to be thrown away and replaced: you just don't know what has happened to somebody else's helmet, as you weren't there to see it.

Should I snag it for cheap or splurge on a new one?

If you believe a helmet is a worth using, buying a new one isn't "splurging". If you don't believe a helmet is worthwhile, why bother at all?

I put some "scuffs" on my spare helmet the other day. It's a couple of years old, and I'm not that careful with my gear, but despite being clipped to the outside of a backpack on a train floor every day it looked no more than grubby.

How did it get scuffed? It was on my head bouncing on the tarmac as I slid across the road when I came off the bike. Nearly all the damage is to the removable brim, but a tiny bit is to the plastic shell. I no longer have a spare helmet.

Lightly-used and scuffs are at odds with each other. There are very few people I would trust to sell me second-hand safety gear, and the only reason I would buy a helmet off any of them is if they snapped up a bargain and found it didn't fit them well enough.

Helmets have a life expectancy of about 3-4 years, you will see if you buy a new one a date on a sticker inside the helmet, this is to let you know when your Helmet was produced and when it should be replaced. Generally, 4 years unless it sees you through a crash.

I dont support the whole idea of expensive helmets because if they do their job right they are one and done. 4 Years is the use by date.

Years ago, Shoei used to run ads for their motorcycle helmets: "Do you need a helmet this good? Depends what you're going to put in it."

'Nuff said. Get a new one.

In general, replace your helmet every five years. If a helmet is getting loose or some of the inner foam or lining is coming out then it’s time to throw it away, whether it has reached the five years or not.

I will not use a 15-year-old helmet if someone gives it for free also. It is a matter of life and death and to be on the safer side buy a brand new helmet. You should not regret buying the old helmet later.

As the technology is advancing all the time and a new helmet is going to provide you a lot more protection and comfort than a 15-year-old helmet.

Despite the commonly held belief in the other comments, a recent study of helmets made between 1987 to 2013 showed that helmets don't actually "go bad" if left on a shelf for a long time.

Our goal was to determine if the impact attenuation properties of bicycle helmet foam changed with age. Based on our tests of foam cores extracted from ten matched sets of 63 helmets between 2 and 20 yrs old, age does not affect the dynamic mechanical properties of the EPS foam liners used in bicycle helmets. As a result, we reject our hypothesis that age affects the impact attenuation properties of the EPS liners used in bicycle helmets. Based solely on impact attenuation properties, we find no support for replacing a bicycle helmet every 2 or more years as suggested by some manufacturers.

Source: http://biomechanical.asmedigitalcollection.asme.org/article.aspx?articleid=2497744

So do a careful inspect and as long as you don't see any visible damage on the helmet, you can go ahead and use it. However, if there is "styrofoam cracking off" as you say then you should probably just toss it.

no most helmets are made single use so if its got damage dont buy unless its like a paint chip