RKI Humidity Filter Disk for PH3 sensor 33-7133 (5/pack)
Description
The RKI Humidity Filter Disk (part number 33-7133) is a required consumable for RKI portable gas monitors equipped with a phosphine (PH3) sensor. Phosphine is a highly toxic gas produced during fumigation operations, phosphide metal reactions, and certain industrial chemical processes. RKI's PH3 electrochemical sensor is sensitive to ambient humidity, and without the humidity filter in place, moisture can cause false readings near 0 ppm — masking a genuine PH3 exposure or triggering nuisance alarms.
Each pack contains 5 filter disks. Replace the humidity filter when it appears discolored, physically degraded, or when your monitor produces erratic near-zero readings despite a clean bump test with calibration gas. Worn filters are a common cause of baseline drift in PH3 sensors and are inexpensive to replace compared to a sensor calibration failure during an active job.
Phosphine is acutely toxic: OSHA's PEL is 0.3 ppm as an 8-hour TWA (29 CFR 1910.1000), with a NIOSH ceiling of 1 ppm. A properly maintained PH3 sensor with a fresh humidity filter is essential for detecting PH3 within OSHA's permissible exposure limit.
For questions about PH3 sensor maintenance or RKI-authorized service, contact PK Safety at
800-829-9580 Monday–Friday.
GX-3R Pro Manual:
Frequently Asked Questions
Why does the RKI PH3 sensor require a humidity filter?
Phosphine electrochemical sensors are sensitive to changes in ambient humidity. Without the filter disk, moisture in the sampled air can interfere with the sensor's electrochemical reaction, producing unstable or false readings near 0 ppm. The humidity filter stabilizes readings by conditioning the air before it reaches the sensor membrane.
How often should I replace the RKI humidity filter disk?
Replace the 33-7133 humidity filter when it is discolored, physically damaged, or when your PH3 sensor produces erratic baseline readings that cannot be resolved by calibration alone. In high-humidity environments — or during frequent outdoor use — you may need to replace filters more often than in controlled indoor settings.
Is the humidity filter required for sensors other than PH3?
The 33-7133 humidity filter disk is specific to RKI's PH3 sensor. Other RKI gas sensors — such as H2S, CO, or O2 — use different filtration or no humidity filter at all. If you are ordering sensors for multiple gas types, verify which sensors require the 33-7133 in your instrument's accessory list.
What is the OSHA exposure limit for phosphine?
OSHA's permissible exposure limit (PEL) for phosphine is 0.3 ppm as an 8-hour time-weighted average (29 CFR 1910.1000). The NIOSH ceiling is 1 ppm. PH3 exposure above these limits requires supplied-air or SCBA respiratory protection. Accurate sensor readings — supported by a functioning humidity filter — are essential for detecting exposures within this range.
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Description
The RKI Humidity Filter Disk (part number 33-7133) is a required consumable for RKI portable gas monitors equipped with a phosphine (PH3) sensor. Phosphine is a highly toxic gas produced during fumigation operations, phosphide metal reactions, and certain industrial chemical processes. RKI's PH3 electrochemical sensor is sensitive to ambient humidity, and without the humidity filter in place, moisture can cause false readings near 0 ppm — masking a genuine PH3 exposure or triggering nuisance alarms.
Each pack contains 5 filter disks. Replace the humidity filter when it appears discolored, physically degraded, or when your monitor produces erratic near-zero readings despite a clean bump test with calibration gas. Worn filters are a common cause of baseline drift in PH3 sensors and are inexpensive to replace compared to a sensor calibration failure during an active job.
Phosphine is acutely toxic: OSHA's PEL is 0.3 ppm as an 8-hour TWA (29 CFR 1910.1000), with a NIOSH ceiling of 1 ppm. A properly maintained PH3 sensor with a fresh humidity filter is essential for detecting PH3 within OSHA's permissible exposure limit.
For questions about PH3 sensor maintenance or RKI-authorized service, contact PK Safety at 800-829-9580 Monday–Friday.
GX-3R Pro Manual:
Frequently Asked Questions
Why does the RKI PH3 sensor require a humidity filter?
Phosphine electrochemical sensors are sensitive to changes in ambient humidity. Without the filter disk, moisture in the sampled air can interfere with the sensor's electrochemical reaction, producing unstable or false readings near 0 ppm. The humidity filter stabilizes readings by conditioning the air before it reaches the sensor membrane.
How often should I replace the RKI humidity filter disk?
Replace the 33-7133 humidity filter when it is discolored, physically damaged, or when your PH3 sensor produces erratic baseline readings that cannot be resolved by calibration alone. In high-humidity environments — or during frequent outdoor use — you may need to replace filters more often than in controlled indoor settings.
Is the humidity filter required for sensors other than PH3?
The 33-7133 humidity filter disk is specific to RKI's PH3 sensor. Other RKI gas sensors — such as H2S, CO, or O2 — use different filtration or no humidity filter at all. If you are ordering sensors for multiple gas types, verify which sensors require the 33-7133 in your instrument's accessory list.
What is the OSHA exposure limit for phosphine?
OSHA's permissible exposure limit (PEL) for phosphine is 0.3 ppm as an 8-hour time-weighted average (29 CFR 1910.1000). The NIOSH ceiling is 1 ppm. PH3 exposure above these limits requires supplied-air or SCBA respiratory protection. Accurate sensor readings — supported by a functioning humidity filter — are essential for detecting exposures within this range.
The RKI Humidity Filter Disk (part number 33-7133) is a required consumable for RKI portable gas monitors equipped with a phosphine (PH3) sensor. Phosphine is a highly toxic gas produced during fumigation operations, phosphide metal reactions, and certain industrial chemical processes. RKI's PH3 electrochemical sensor is sensitive to ambient humidity, and without the humidity filter in place, moisture can cause false readings near 0 ppm — masking a genuine PH3 exposure or triggering nuisance alarms.
Each pack contains 5 filter disks. Replace the humidity filter when it appears discolored, physically degraded, or when your monitor produces erratic near-zero readings despite a clean bump test with calibration gas. Worn filters are a common cause of baseline drift in PH3 sensors and are inexpensive to replace compared to a sensor calibration failure during an active job.
Phosphine is acutely toxic: OSHA's PEL is 0.3 ppm as an 8-hour TWA (29 CFR 1910.1000), with a NIOSH ceiling of 1 ppm. A properly maintained PH3 sensor with a fresh humidity filter is essential for detecting PH3 within OSHA's permissible exposure limit.
For questions about PH3 sensor maintenance or RKI-authorized service, contact PK Safety at 800-829-9580 Monday–Friday.
GX-3R Pro Manual:
Frequently Asked Questions
Why does the RKI PH3 sensor require a humidity filter?
Phosphine electrochemical sensors are sensitive to changes in ambient humidity. Without the filter disk, moisture in the sampled air can interfere with the sensor's electrochemical reaction, producing unstable or false readings near 0 ppm. The humidity filter stabilizes readings by conditioning the air before it reaches the sensor membrane.
How often should I replace the RKI humidity filter disk?
Replace the 33-7133 humidity filter when it is discolored, physically damaged, or when your PH3 sensor produces erratic baseline readings that cannot be resolved by calibration alone. In high-humidity environments — or during frequent outdoor use — you may need to replace filters more often than in controlled indoor settings.
Is the humidity filter required for sensors other than PH3?
The 33-7133 humidity filter disk is specific to RKI's PH3 sensor. Other RKI gas sensors — such as H2S, CO, or O2 — use different filtration or no humidity filter at all. If you are ordering sensors for multiple gas types, verify which sensors require the 33-7133 in your instrument's accessory list.
What is the OSHA exposure limit for phosphine?
OSHA's permissible exposure limit (PEL) for phosphine is 0.3 ppm as an 8-hour time-weighted average (29 CFR 1910.1000). The NIOSH ceiling is 1 ppm. PH3 exposure above these limits requires supplied-air or SCBA respiratory protection. Accurate sensor readings — supported by a functioning humidity filter — are essential for detecting exposures within this range.
Specifications
Specifications
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