| 摘要 |
A filter change indicator is provided and includes a fragrance and auditory emission apparatus adapted to be installed in disposable-type air filters utilized to remove contaminants carried along in the air stream of HVAC systems. The fragrance and auditory emission apparatus functions to emit a shrill tone or whistling noise when the air filter becomes dirty or clogged. The fragrance and auditory emission apparatus also functions as an air freshener or a room deodorizer.
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