Fowler Associates Labs

Response from the ESD Journal Expert

Yes, it is dangerous since you are on a scaffold.  We have investigated people falling off ladders due to vacuum hose charging.Yes, it is dangerous since you are on a scaffold.  We have investigated people falling off ladders due to vacuum hose charging.

The phenomena is that the beads are charging as they go though the hose.  The hose is rubber so it does not get rid of the charge through conduction since it is insulative and can not conduct the charges away.  Your hand is charged by induction (being near the charged rubber) and then you discharge when you touch something metal or just come close to something metal.

The solution is that everything you are holding must be metal and must be grounded or at least connected to something large and conductive like the scaffold.  This will make the charges flow away from the hose.

Can you put a metal tube on the end of each of the hoses you are using and run a wire from the metal tube or hose to the scaffold and hopefully to ground?  You could use conductive rubber hose for the system.  Hose such as is used for the transfer of volatile liquids like gasoline. If not,  take some of the metal tape like is used for air conditioning and heating duct repairs.  This is usually aluminum foil with adhesive on it.  Wrap both hoses with the tape especially where you are in contact with them.  Connect a wire to the scaffold and to ground if possible by a hose clamp.

This makes the voltage fields "short" to ground before they influence you. Remember it must be conductive to be grounded.  You can not just run a wire to an insulative rubber hose. Also remember, the part you are touching or near must be conductive and grounded.

I hope this helps.  Just don't fall off the scaffold. 

The phenomena is that the beads are charging as they go though the hose.  The hose is rubber so it does not get rid of the charge through conduction since it is insulative and can not conduct the charges away.  Your hand is charged by induction (being near the charged rubber) and then you discharge when you touch something metal or just come close to something metal.

The solution is that everything you are holding must be metal and must be grounded or at least connected to something large and conductive like the scaffold.  This will make the charges flow away from the hose.

Can you put a metal tube on the end of each of the hoses you are using and run a wire from the metal tube or hose to the scaffold and hopefully to ground?  You could use conductive rubber hose for the system.  Hose such as is used for the transfer of volatile liquids like gasoline. If not,  take some of the metal tape like is used for air conditioning and heating duct repairs.  This is usually aluminum foil with adhesive on it.  Wrap both hoses with the tape especially where you are in contact with them.  Connect a wire to the scaffold and to ground if possible by a hose clamp.

This makes the voltage fields "short" to ground before they influence you. Remember it must be conductive to be grounded.  You can not just run a wire to an insulative rubber hose. Also remember, the part you are touching or near must be conductive and grounded.