This reusable card can accurately measure ultraviolet (UV) radiation accurately in 10 seconds. Check the lamp that is in use by placing the card on the spot under the UV lamp (within 5 cm from the lamp). The reaction area on the test card shows purple indicating that the bulb contains UVB values. If the card does not show any color, change the bulb usually every 6-8 months and the card can be used up to 500 times when used in 10 second increments. When not in use, please put the card in a holder or store in a dark place.Card measures 3.39" x 2.13".
