UL now certifies horticulture PAR Mapping. The setting of standards helps shape and form any industry’s level of quality or attainment. Standards govern the quality, safety, level, grade, caliber, merit and excellence of products or services to meet a minimum of set of values people can expect from that type of product or service including LED lighting.

The history of horticulture performance metrics started out very ambiguous and the most growers had to go off was wattage and spectra.  This combination was misleading though as the amount of photonic energy was not measured.   So higher wattage and spectra became the standard until photon measurements using quantum meters became available.
Companies like Smart Grow and Fluence Bioengineering pioneered a testing metric call par mapping by taking quantum measurements of micromoles (symbol μmol 106 moles) per second at various places over an entire grid.  (PPFD)  These PAR map grids started out as 4 x 4 area.  Par Mapping was the first metric available that showed growers what the distribution of light was over an area.  Smart Grow and Fluence Bioengineering would video quantum meter readings at multiple distances and post their results.  These new results were very useful however they did not have the credibility from a valued third party.   More tests were done by third party organizations such as retail stores however they still lacked the credibility of an official sphere report.
Horticulture relied on LM-79 reports from companies like UL and Intertek however they measured lumens rather than PAR light.  The addition of the new UL certification is something EVERY grower needs to be aware of before they make their buying decision.  Finally growers can eliminate the noise around whether a par map is valid and obtain real metrics they can count on when planning their grow.  Especially the breakdown of photon radiometric flux % output in the all important Orange and Red nm range.  This range is CRITICAL when it comes to flowering cannabis.
In November 2016 UL announced the beginning of horticulture reporting.
To address the needs of manufacturers that offer lighting equipment for the horticultural industry, UL established a new safety Certification category for Horticultural luminaires: IFAU. This new category offers manufacturers of horticultural lighting a way to clearly distinguish their UL Listed specialty lighting equipment from those Certifications applicable to lighting intended for general illumination of indoor and outdoor spaces.

SmartGrow System’s GOLDENi and Baby Blue units are Underwriters Laboratories (UL) certified

With UL certification, commercial grow operations and indoor farms across the United States and Canada can install GOLDENi and Baby Blue while meeting or exceeding their building regulations.
UL horticulture requires metrics and test procedures that are quite different from those used for products intended for the human visual system. 
 Quick Links
PAR Map example
Smart Grow’s Sphere Reports for Certification

Differences Between Horticultural and Traditional Light

Most people are familiar with the concept of light output and intensity, but what we are familiar with as humans is largely from the perspective of photopic vision. This is based on the average human eye response (known as the photopic curve) with metrics such as lumens and lux weighted according to this curve. The photometric curve peaks in the yellow-green region and drops off towards both the blue and red ends of the spectrum.; however, this response curve is not applicable to plants, as they do not have eyes.

Rather than reference the photopic response curve, horticultural lighting references the photosynthetic response region (typically referred to as Photosynthetically Active Radiation, or PAR) as a more appropriate reference. Also referenced by some is the McCree Curve, which was developed based on CO2 assimilation per mole of photons between 400nm and 700nm wavelengths. This widely referenced curve has peaks in the blue and red range.

Spectral Power Distribution

Selecting the best spectral power distribution is not a simple matter. When light affects the growth characteristics of a plant, it is known as phototropism. At its most basic, phototropism can cause a plant to grow towards or away from a light source, but additional growth changes are possible. The same is also true with spectrum. As noted earlier, a spectrum heavier in reds tends to make plants grow longer stems, and a spectrum heavier in blues encourages leaf growth. While these colors may seem obvious given the McCree Curve, other studies have shown that supplementing these colors with green light (up to a certain point) will enhance growth for some species, further supporting the need for multiple spectrums of light for optimal plant growth.

It stands to reason that to get the best out of a crop of plants, there may be a specific light formula that is appropriate, and that light formula may change over time depending on what the desired growth of the plant is and what stage of the plant lifecycle it is in. With HID lamps, changing the spectrum is possible with certain ballasts by swapping out a metal halide lamp for a high pressure sodium lamp, or vice versa. This is limited, however, to the spectrums that can be made with these technologies. With fluorescent lamps, switching to different phosphor combination lamps can achieve this as well, but with similar limitations to the number of available options. Multi-source LEDs have the potential to offer a wider range of tenability by using multiple direct color LEDs (potentially including UV and IR) and/or including some phosphor-converted white LEDs for a wider spectrum of light. The ‘right’ recipe of light for a plant will depend on the specific species, and this information can be closely guarded as a competitive advantage.

GOLDENi 600 PAR Report

Enhanced spectra output breaks out all measuring in nm ranges from UV to IR.
Enhanced spectra output
See full report for GOLDENi 600:
New Metrics Added for horticulture

The sheer number of metrics that can be associated with visible light can get confusing, and with horticultural lighting this is no different. To reiterate an earlier point, lumens (and lux, candela, etc.) are all adjusted for the human eye response and, as such, are not an appropriate reference and should not be considered when evaluating a fixture for horticultural applications. The primary metrics for horticultural use are focused on the quantities of photons produced (typically measured in micromoles, or 6.022×1017 photons per micromole) as these are what get absorbed by the plant. Though others can be explored, the most common metrics are listed below:

Photosynthetic Photon Flux (PPF) – This metric is the unweighted photon flow in micromoles per second, but not necessarily in any one direction. This would be somewhat analogous to lumens, as it is an overall quantity.

Photosynthetic Photon Flux Density (PPFD) – A density based metric that focuses on how many moles hit one square meter per second. This would be similar to a lux, where it is the quantity hitting a specific area.

Daily Light Integral (DLI) – This metric involves the number of moles of photons that hit a surface over a 24 hour period.

Additional metrics and definitions are being worked on by organizations such as the American Society of Agricultural and Biological Engineers (ASABE), as are the test methods which are used to acquire these measurements. One such potential metric expands the wavelength range beyond photosynthetically active radiation and could include the ranges in UV, far-red and infrared to which plants are also sensitive.
Performance Testing
Having the right spectrum and quantity of light at the right point in the plant lifecycle can make a significant difference in the quality of the end product (i.e. can influence plant growth characteristics). UL now also offers measurement of horticultural lighting equipment by leveraging our custom industry specific test report to provide an objective measure of performance. This report includes the following key metrics a grower needs to select the best light source for their product:
  • A 350-800nm spectral distribution, acknowledging chlorophyll is not the only photoreactive chemical in plants, to illustrate a better picture of what light output a product is providing
  • Photosynthetic photon flux (PPF) binned into 10 nm ranges to better illustrate the spectrum
  • PPF output and efficacy
  • Optional photosynthetic photon flux density (PPFD) distribution information

UL Safety

UL Certified is the "Recognized Component Mark" is a type of quality mark issued by Underwriters Laboratories.Businesses, consumers and regulatory authorities around the world recognize the trusted rigor and technical excellence of UL certifications. Backed by more than a century of proven safety science expertise, UL certifies your products and writes the Standard the industry has come to trust. Horticultural lighting equipment is evaluated to the requirements in UL 8800, the Outline of Investigation for Horticultural Lighting Equipment. 

Other certification programs
Intertek has introduced a Horticultural Lighting Certification Program to help manufacturers develop products that comply with the safety and performance requirements unique to horticultural lighting. The product testing firm points out that in North America, horticultural lighting products do not have any safety and performance standards specific to them. For this reason, Intertek has devised a unique certification program to guide lighting makers through all applicable requirements. This certification program conducts tests according to multiple current standards and looks at those in development.
Heading Toward the Future
The setting of standards helps shape and form any industry’s level of quality or attainment. Standards govern the quality, safety, level, grade, caliber, merit and excellence of products or services to meet a minimum of set of values people can expect from that type of product or service including LED lighting.
Commercial growing operations are expanding at a rapid pace throughout North America. As UL and the lighting industry work to develop and bring safe lighting equipment to this rapidly advancing market, they are collectively learning that not all of the current safety requirements that exist for general illumination lighting are appropriate for horticultural lighting. On the other hand, additional considerations are needed to address the different installation and wiring practices; severe environmental conditions such high humidity, dust, chemicals vapors and elevated ambient temperatures; and unique/tunable light output characteristics (intensity and wavelength) associated with horticultural lighting.
The goal is to keep the main players in these industries involved to cumulate the cutting edge knowledge and allow these standards to evolve and keep pace with the new products of these industries.  Make sure you purchase only UL Certified lighting systems.

Donna Ebeling About Donna Ebeling
Gardening had always been my passion, until I learned about organic gardening. That's a whole new ballgame. So when I was asked to write for this blog, I jumped at the opportunity to research, to learn more about organic gardening and to write about that and other plant-related topics. Thank you for being here, I hope you enjoy these articles at least half as much as I do writing them!