There are only a handful of UVC lamp manufacturers, yet there is a rapidly increasing number of manufacturers of equipment using uv light for sterilization, disinfection, air purification, and HVAC coil irradiation. Each of these folks want you to get the replacement bulbs from them which has lead to a lot of mis-information and, unfortunately, a race to specilization instead of standardization increasing the cost of replacement uv bulbs.Wanting to create a custom product that ties a customer to purchase replacement parts only from you is not a new idea among equipment maufacturers, and the booming UVC light business is no different. This is why it is critical that when evaluating UVC systems attention is paid to whether or not the system uses commercially available parts, or if you are handcuffed into buying only from the OEM for replacement parts.
The Myth of Higher Output Lamps
Yes, there are high-output and standard-output lamps; but those that claim to be exponentially higher than a competitor lamp is either comparing a high-output bulb to standard-output bulb or "massaging" the data. This confusion stems from when UV-C was first used for coil irradiation and neon was added to some lamps. The neon created a higher bulb temp which increased UV-C output, but it also caused the output to drop faster and burn up the filiments quicker leading to more failures. This process is all but gone as only a very small amount of lamps for very specific applications use this added neon. The reason for not using this anymore is two-fold; first the cost of neon sky-rocketed so it hurt the affordability of the lamps and when some manufacturers didn't use neon they could warranty lamp life. The fact is: a watt is a watt and if you are getting your replacement UV bulbs from the OEM you are probably paying more than you need to.
Notice the Lamp Ends
Because the vast (90+ percent) majority of UVC Lamp manufacturing is done by Phillips and GE the easiest way equipment manufacturers can lock you into buying replacement parts from them is to modify or add a pigtail to an off the shelf bulb. This problem is rampant among both the residential and commercial applications. Traditional/commercially available lamp ends will be either a dual ended bi-pin or single ended square 4-pin design - single pin have a little less availablity but are around from multiple sources, while any lamp with a rubber pigtail, hard plastic fitting, or odd pin arrangement are all modified or specialty lamps that don't do anything for the effectiveness of the system and exist only so you have to buy the replacements from a sole source.
Additional lamp options are the type of glass and if there is a protective sleeving over the glass portion of the lamp. Glass is an important part to make a bulb one that emits Ultraviolet C Band light, as all fluorescent lamps produce this germicidal light but it can not penetrate the glass. Quartz glass is the overwhelming favorite among germicidal lamp manufacturers, but some do elect to use sodium-barium silicate (also known as "soft-glass" lamps), there is no performance advantage of one over the other it is simply a matter of preference. Also to be decided is if you want to use "sleeved" lamps or not.
Sleeved lamps are encapsulated with teflon that will remain in-tact if the bulb were to break. This keeps all of the glass shards and any remaining mercury from creating a mess. If the lamps are used for HVAC coil irradiation it also prevents the glass and mercury from being blown into the ductwork of the HVAC system. Some manufacturers have a large upcharge and worse lead times on sleeved lamps, while some are more reasonable so depending on your application and who you buy from the sleeved lamps may or may not be worth the added cost.