Can I use silicone to protect the BIOS

I plan to create an airgapped laptop with a seperate bootloader that is on a permanently write protected SD card that i will cary on my pocket all the time.

I will also remove the wireless card on the motheboard. Only thing that makes me unsettled is the BIOS. It’s a pretty old BIOS and doesn’t even support UEFI.

I can’t be sure about it’s integrity so I thought can’t I just pour silicone to protect the BIOS chip? To prevent flashing new firmware I can just use a hard password.