Radiation Leakage of Before-Sale and Used Microwave Ovens

Results and Discussion

Before-Sale Ovens

None of the before-sale units showed any visible damage other than minor enamel abrasions.

However, a total of six before-sale ovens from three different manufacturers were found to be in non-compliance with the labeling requirements. All manufacturers whose ovens were labeled incorrectly were contacted and were required to implement correct labeling on new oven models offered for sale, lease or importation into Canada. In all cases, affected manufacturers took immediate corrective action to comply with the Radiation Emitting Devices Regulations. The microwave power of these units ranged from 580 W to 1000 W.

The results of radiation leakage measurements of before-sale ovens with and without load are shown in Figure 1. Each point on these plots represents the maximum microwave emission from one oven.

Descriptive statistics with respect to radiation leakage are listed in Table 1. It may be seen that the average levels of radiation leakage with and without a water test load were 0.08 and 0.3 mW/cm², respectively. These levels are well below the respective limits of 1 mW/cm² and 5 mW/cm², as specified in the regulations. Based on data in Table 2, a higher percentage of the surveyed ovens show a maximum leakage at the center of the door screen.

Table 1: Descriptive statistics on radiation leakage from the surveyed ovens

Before-Sale (60 models)

Statistics	No Load (mW/cm2)	Load (mW/cm2)
Maximum	1.5	0.4
Minimum	0.04	0.001
Average	0.3	0.08
Std. Dev.	0.28	0.07
Regulatory Limit	5	1

 

Used (103 models)

Statistics	No Load (mW/cm2)	Load (mW/cm2)
Maximum	5	4.5
Minimum	0.03	0.01
Average	0.52	0.17
Std. Dev.	0.77	0.45
Regulatory Limit	5	1

Used Ovens

In the case of used ovens, some of the labels were no longer affixed to external surfaces due to age. The microwave power of these ovens ranged from 400 W to 1400 W, with an average value of 667 W.

The results of radiation leakage measurements of used ovens with and without load are shown in Figure 2. Each point on these plots represents the maximum microwave emission from one oven. Descriptive statistics with respect to radiation leakage are listed in Table 1. It may be seen that the average levels of radiation leakage with and without a water test load were 0.17 and 0.52 mW/cm², respectively. These average levels are well below the microwave radiation leakage limits specified in the regulations. Similar to the case for before-sale ovens, the majority of used ovens shows a maximum leakage at the center of the door screen. As shown in Figure 2, one oven model was observed to have a maximum leakage of 4.5 mW/cm² when tested with a water load. The oven was 23 years old at the time of the survey. In contrast, a 22-year-old used oven emitted leakage well within the regulatory limit when tested with and without a water load. Thus, age is not the primary factor for excessive microwave leakage.

Table 2: Positions of maximum leakage around the surveyed ovens expressed in percentage of ovens.

Leakage Positions	Before-Sale Water Load	Used Water Load	Before-Sale No Load	Used No Load
Door Frame: Right	11.7%	10.6%	8.3%	1.0%
Door Frame: Top	1.7%	15.4%	1.7%	18.6%
Door Frame: Bottom	11.7%	7.7%	11.7%	8.3%
Door Screen: Top	5.0%		5.0%	1.0%
Door Screen: Bottom	13.3%	1.9%	15.0%	4.1%
Door Screen: Center	51.7%	38.5%	51.7%	43.3%
Cabinet: Top	3.3%	1.9%
Cabinet: Timer	1.6%	17.3%	3.3%	10.3%
Door Release		6.7%	3.3%	13.4%
Sum	100%	100%	100%	100%

Figure 2. Graph showing leakage data of used ovens with and without load.