Heat sources for Chicks

If it has a heavy smell, I would be worried too.
The traditional heat lamp is a good standby.
Was wondering if you had seen @Blooie articles on using a heating pad for brooding. It may be at least another option for you if you are running out of time.

https://www.backyardchickens.com/t/956958/mama-heating-pad-in-the-brooder-picture-heavy-update

https://www.backyardchickens.com/a/yes-you-certainly-can-brood-chicks-outdoors

Here's one by @aart which is similar as well.
https://www.backyardchickens.com/a/pseudo-brooder-heater-plate

And a heating pad is half the cost of those other heaters and can be used for other purposes, like cold human feet, when the chicks are done with it.

You are very wise NOT TO use that heater! I would assume as you would that the fumes could possibly be toxic to the chicks!I'm very glad you noticed the smell! I've always just used the "old fashioned" metal heat lamp with the ceramic light base and the large traditional red heating lamp. I bought a adjustable heat lamp stand that can be moved up and down so when it comes time to drop the temperature the lamp can EASILY be adjusted to accommodate the temperature needs. I know it's not fancy or new, but it works. I have also looked at the nice new fancy brooder but they are too pricey for me. I've heard nothing but good things about them but for now, unless I can get ahead I'm going to have to stick to the "old fashioned" way to heat the brooder. it does work so that's what matters. I would talk to the company who sold you the heater and INSISTING they give me a refund! There IS a reason it's giving off fumes! could be a coating melting or plastic melting? what ever reason I wouldn't chance it. Your smart NOT to brood with it!! You should be allowed a refund! What ever new method you decide as a heat source, I wish you the best with healthy happy chicks!