No, it is not required to wear a respirator when applying Senguard, however, you must provide good ventilation by opening multiple windows. Senguard has some fumes..... kind of like finger nail polish remover or paint thinner for example. However, if in a small room or closed space such fumes can become potent causing dizziness, etc.

  

The instructions do suggest wearing a respirator for this reason.... to ensure people take precautions like wearing gloves and protective eye wear. This only makes sense when using any chemical. 


Even when using common household cleaners you must guard against excessive or prolonged skin exposure and contact with eyes. So, these recommendations are just common sense precautions and not because Senguard is so much more toxic and dangerous than say acetone.

You could wear a respirator if fumes bother you, but if you provide good air flow, the fumes should not be a problem and dissipate quickly as the sealer cures. Keep windows open for a few hours after application will speed this process.