There is a law (either NY or Federal) requiring children’s pajamas to be flame resistant to some degree. They are either treated, or cannot be from certain materials, I am not sure about the details of the law.

It makes sense that when you buy a beged for your child that is supposed to ‘protect him’ on a ruchnius level, you should try to avoid a material that endangers him on a physical level! Stick to 100% cotton, or pressure the manufacturers to treat them to make them flame resistant.

BTW – I am not familiar with R’ Moshe’s psak, but it seems to me that synthetics might be potur from Tzitzis, in which case you are missing the mitzvah, but why would they be ‘forbidden’ to wear?

From a fabric finishing site:

“All fabrics will burn with some being more combustible than others. Untreated fabrics such as cotton, linen and silk burn more easily than wool, which is more difficult to ignite and burns with a low flame velocity.”

“Most synthetic fabric, such as nylon, acrylic or polyester resist ignition. However, once ignited, the fabrics will melt. This sticky, hot, melted substance will cause localized and very severe burns. When natural and synthetic fibers are blended, the hazard may increase due to the combination of a high rate of burning and melting usually will result in serious burns. In some cases, the hazard may be greater than that of either fabric individually.”

I am very sensitive and feel terrible about what happened.

But why aren’t you sensitive to the daily bracha l’vatallah and Hashem’s name being mentioned in vein by so many innocent people every single day.

The neighborhood where this happened is probably a litvishe neighborhood who live by the word of our Poskim, especially Reb Moshe zt”l.

In the past, everyone knew there was an issue with mesh-tzitsis. However, in recent years, these tzitzis are being marketed in our neighborhoods and they look like cotton. Customers do not realize there is any issue at all with them. It is probably safe to say that thousands of people are wearing these tzitzis without realizing. Besides not fulfilling the mitzvah, there is a serious issue with a bracha l’vatalah.

I am not one to say why this happened, but it is not so we can just say “OY VEY!” We could and should learn at least this obvious lesson.