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Safe Disposal of Mercury Displacement Relays


Watlow developed this procedure for properly disposing of MDRs to be a good steward of the environment and comply with applicable laws.


By returning your Watlow MDR to an approved mercury recycler you can be sure that the MDR will be recycled or disposed of properly. However, the recycler will charge a recycling fee.


Mercury Displacement Relay (MDR) - An electromechanical switching device having one or more poles that contain metallic mercury and a plunger which, when energized by a magnetic field, moves into a pool of mercury, displacing the mercury sufficiently to create a closed electrical circuit.



• MDRs must not be placed in the waste stream until the mercury is removed for recycling.
• Please contact Retrofit Recycling at 507-455-2181 or www.retrofitcompanies.com to obtain a quotation for your recycle job.
• MDRs eligible for this service are Watlow Series A, H, HG, KD, L, LD, M and MD relays.

Hazardous Materials

If the MDR you wish to recycle has one or more breached (open) poles, you must seal it in a non-porous container to prevent the escape of liquid and gaseous mercury. Acceptable non-porous containers are composed of high density polyethylene, or equivalent.


Watlow recommends the relay(s) be double-bagged in sealed Zip-Lock®-type storage bags and further sealed with heavy-duty packaging tape. Ship the unit with adequate packing material in a corrugated cardboard box (minimum burst strength of 20 pounds). Breached relays must be shipped as hazardous material.


Please include the following information on the hazardous material shipping label:

    • Proper shipping name: Mercury contained in manufactured articles
    • Emergency contact number: 507-454-5300
    • Hazard Class or Division: 8
    • Identification Number: UN2809
    • Packing Group: 1 for air transport
    • Packing Group: 3 for ground transport
    • Type Label(s) and required information: Corrosive

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