Most airborne particles are positively charged, and most electrostatic speakers have a negative charge on the diaphragm (which attracts these airborne particles). An electrostatic air cleaner uses negatively charged electrodes specifically because they are so effective at attracting dust particles. Because of this phenomenon, many electrostats either have a thin mylar dust cover or an automatic shut-off circuit. Neither is an ideal solution.
The electrostats I own and sell, Sound Labs, use a different and (in my opinion) more elegant apprach. Sound Labs use a positively-charged diaphragm, which of course repels positively-charged airborne particles. This allows Sound Labs to get away without a dust cover, and since they can stay fully charged up all the time they always sound their best.
Sound Lab has speakers over a dozen years old in the homes of smokers that have never needed any service. While the speakers might be marginally happier in a totally smoke-free environment, the presence of cigarette or cigar smoke seems to have no practical effect on either the life or performance of the Sound Labs. They just smell a little funny and are a bit harder to sell to a non-smoker.
If you catch a ray of sunlight right in front of a Sound Lab speaker, you can see the dust particles kind of drifting around in the ray. Those particles that drift too close to the speaker will suddenly shoot away, having encountered the positive-charge field. In fact, over time you can actually get a dust buildup on the floor in front of a pair of Sound Labs from the particles that have been repelled, or so I've been told by one owner!
