Performance monitoring of gas-phase air filters

A method for monitoring the performance of a gas-phase filter positioned in an air stream, which may be subject to molecular contamination, and useful for removing molecular contamination therefrom, said method comprising the steps of:

• exposing an upstream detection surface to the airstream at a location upstream of the air filter so that a variety of upstream molecular contaminants may form non-volatile residue on the exposed upstream detection surface over time;
• providing a first electrical signal representative of the mass of non-volatile residue formed on the upstream detection surface;
• exposing a downstream detection surface to the airstream at a location downstream of the air filter so that a variety of downstream molecular contaminants may form a non-volatile residue on the exposed downstream detection surface over time;
• providing a second electrical signal representative of the mass of non-volatile residue formed on the downstream detection surface;
• and
• determining in real-time the performance of the air filter based on the first and second electrical signals that are provided.

A filter monitor for determining the performance of a gas-phase filter positioned in an air stream, which may be subject to molecular contamination, and useful for removing molecular contamination therefrom, said filter monitor comprising:

• an upstream piezoelectric detector having a detection surface exposed to the airstream at a location upstream of the air filter so that molecular contamination may form a nonvolatile residue on the exposed detection surface of the upstream detector, said upstream detector having an output for providing a signal representative of the increase in mass of non-volatile residue formed on the detection surface of the upstream detector;
• a downstream piezoelectric detector having a detection surface exposed to the airstream at a location downstream of the air filter so that molecular contamination may form a non-volatile residue on the exposed detection surface of the downstream detector, said downstream detector having an output for providing a signal representative of the increase in mass of non-volatile residue formed on the downstream detector;
• and
• a comparator having an input coupled to said upstream and downstream detectors and having an output for providing an output signal representative of the performance of the air filter based on the ratio of signals received from said upstream and downstream detectors.

A filter monitor for determining the performance of a gas-phase filter positioned in an air stream, which may be subject to molecular contamination, and useful for removing molecular contamination therefrom, said filter monitor comprising:

• an upstream piezoelectric detector having a detection surface exposed to the airstream at a location upstream of the air filter so that molecular contamination may form a non-volatile residue on the exposed detection surface of the upstream detector, the detection surface of said upstream detector being selected so that the increase in mass of non-volatile residue formed on the detection surface of the upstream detector may be determined;
• a downstream piezoelectric detector having a detection surface exposed to the airstream at a location downstream of the air filter so that molecular contamination may form a non-volatile residue on the exposed detection surface of the downstream detector, the detection surface of said downstream detector being selected so that the increase in mass of non-volatile residue formed on the detection surface of said downstream detector may be determined;
• and
• means for determining the performance of the air filter based on the mass of non-volatile residue formed on the upstream detection surface and based on the mass of non-volatile residue formed on the downstream detection surface.