Contamination Monitoring

Contamination control is a primary emphasis of the radiation safety program at Northeastern University. Prudent contamination control involves careful planning, process containment, protective coverings, personal protective equipment, and avoidance of spills. However, contamination monitoring is the most important element of a contamination control program. Routine contamination monitoring at NU is accomplished through a variety of contamination surveys.

Daily Monitoring

Daily monitoring is to be done anytime a Radioactive Material (RAM) experiment is performed. A portable survey meter is acceptable as long as the sensitivity of the instrument allows for efficient detection of the radionuclides used. See chart at the bottom of this Fact Sheet.

Click on probe type for instructions on how to use the meter. 44-88, 44-9, 44-7 or 44-3

  • Each day RAM is used, a daily containment survey is required. Results of surveys must be recorded in mR/hr on the survey form.
  • Those using H-3 must conduct a wipe test and record the results in DPMs. A survey meter cannot detect the presence of tritium.
  • Exception: A “NO WORK” entry must be made on days where no work is performed.

A daily survey should cover the hands, lab coat, shoes (top and bottom), work area, floor adjacent to the work area, floor of exit doorways, exit door knobs, and potentially contaminated equipment.

  • Any area found to be contaminated must be decontaminated immediately, re-surveyed and recorded on the Spill Documentation Form.

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Weekly Survey

A thorough contamination wipe survey of the lab is required to be performed every week in addition to daily monitoring during experiments. This weekly survey is to be completed even if NO work is done during the week and must be recorded in DPMs on the area survey form.

A minimum of five locations must be surveyed, including at least one wipe on the floor near the doorway. Wipe locations should include areas and items that have a higher potential for contamination. Locations should be varied from week to week. Some suggested areas to wipe for contamination are:

  • Work areas, lab benches, and desks
  • Lab equipment used with radioactive materials
  • Refrigerators and freezers
  • Incubators
  • Floor adjacent to work areas and near hallway entrances
  • Door handles

Wipes must be counted by an appropriate counting technique (LSC or gamma counter). To analyze a wipe with a survey meter click on probe type. 44-88, 44-9, 44-7 or 44-3

Weekly surveys (whether analyzed with a LSC, gamma counter or survey meter) must be documented on an area survey form in DPMs.

If a wipe test reveals contamination exceeding 200 DPM/100 cm2, decontaminate the area and test again. Be sure to fill out a Spill Documentation Form.

Note: Analyzing a wipe with a survey meter can only be performed with approved isotopes. See chart at the bottom of this Fact Sheet.

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Recordkeeping Requirements

All labs are required to have a Radiation Program binder. The following paperwork must be kept in the binder:

Inventory Sheet

  • One inventory sheet for each RAM stock vial
  • Updated every time RAM is withdrawn from stock
  • Accumulation of RAM waste must also be logged

Updated Lab diagram

Area Survey Form

  • Daily Surveys- Write “NO WORK” on days RAM is not used
  • Weekly Surveys

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Signature Requirements

Daily. Each day RAM is used. A laboratory worker must conduct a survey, document the results and initial the survey records.

Weekly. PI or AI must sign the survey form once a week. “No work” must be written for all days no RAM work was done.

The signature documents that the PI/AL reviewed both the inventory and survey records and resolved any issues with the laboratory staff.

Monthly. PI must sign the survey form at least once a month. The signature documents that the PI reviewed both the inventory and survey records and resolved any issues with the laboratory staff.

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Inactive Status

If a RAM experiment is not planned in the near future the PI can place the lab in “inactive” status once EHS has the isotopes secured under their supervision. If there is no inventory in the laboratory, there are no documentation requirements. Contact EH&S x2769 or

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Survey Instrument Requirements


Isotope Daily-When RAM is used Weekly-Done regardless of work
Probe Requirements Recorded in mR/hr Counter/Meter Requirements Recorded in DPMs
P-32, P-33, S-35, In-111, Tc-99m, Cr-51 Geiger-Mueller (G-M) detector 44-9, 44-88 Liquid Scintillation Counter (LSC) or survey meter Procedures for Analyzing a Wipe Using a Meter
I-125 NaI Solid Scintillation detector 44-3 Gamma counter or survey meter.
C-14 Mueller (G-M) detector 44-9,44-88 LSC
H-3 LSC Record results in DPMs Cannot detect H-3 with a survey meter. LSC


When using a portable survey meter, a count rate of more than two times the background typically indicates the presence of contamination.

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