MMS production expired date/ smell???

I have been producing MMS from powder Clean Pool Sodium Chlorite 80% for my self two times (within 2 years). All was ok, worked fine.
However I did it again today but I felt an odour/smell from the powder. I read somewhere that powder (Soidum Chlorite) shoudl withstand up to 10-20 years but this is odourless. I do not remember did I feel this smell/odour at previous 2 times.
I bougt it roughly 2,5 year ago. I Can not find an expired date.

Is it possible is reached expired date and shouln not be used??

Please advise as I am going to pourit to bottles today.

Many thanks

I have clarified a bit what written above.

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I have been producing MMS from powder Clean Pool Sodium Chlorite 80% for my self for two years (two times). All was ok, worked fine so far.
However I did it again today but I felt an odour/smell from the powder.
I read somewhere that powder (Soidum Chlorite) should withstand up to 10-20 years and that normally this is odourless.
But now I can smell it. I do not remember did I feel this smell/odour at previous 2 times.
I bougt it roughly 2,5 year ago. I Cannot find an "expire date".

Is it possible this Sodium powder reached expire date and it should not be used??
Colour is fine - yellow fish. Only this smell of powder ....

Please advise as I am going to pour it into bottles today.

Many thanks
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Many thanks for response!

Powder was/ is stored in room temperature in an oryginal plastic box, covered and wrapped in black plastic bag.

I have opened the powder again while ago and waited 30s-1min; smell seem was disapearing and it indeed could be plastic smell not powder.
I have asked my wife while ago and she confirmed as this could be more plastic than powder indeed (she is more sensitive).

During production colour was fine- yellow fish. I poured made NaClO2 into bottles.
I tried it 2 times on teeth brushing. Smell after mixing with citrid acid the same as normally, taste seem to be same.
Hmm, maybe you right and this is plastic.
I would not think that way.
Have you met with this issue already?

Many thanks for great spot!!!!

Many thanks!! I am more ensured right now, that this is all fine and as you suggest I will store it in a glass jar or something to avoid in future any concerns.