I will not comment on the need for respiratory protection but keep in mind the potential for skin exposure. Isocyanates are skin sensitisers. There is also evidence that skin exposure can result in a respiratory reaction. There is also evidence that for many skin sensitisers airborne exposure to the chemical can result in a skin (and possibly respiratory) reaction at exposure levels below that of the Workplace Exposure Limit.

"Although respiratory exposures have been the primary concern with isocyanates, skin exposure can also occur and may contribute to sensitization and asthma." -  Skin Exposure to Aliphatic Polyisocyanates in the Auto Body Repair and Refinishing Industry: A Qualitative Assessment, Liu Y et al, Annals of Occupational Hygiene, 2007, 51, 429-439

 “Direct transdermal uptake from air is not routinely considered. Yet the studies outlined in the previous paragraph suggest that, for at least some indoor pollutants, direct dermal uptake from air may occur at rates that are comparable to or larger than inhalation uptake.” – Weschler CJ, Nazarofi WW, Dermal Uptake of Organic Vapors Commonly Found in Indoor Air, Environmental Science & Technology, 2014, 48, 1230-1237

“Direct transdermal uptake from air is not routinely considered. Yet the studies outlined in the previous paragraph suggest that, for at least some indoor pollutants, direct dermal uptake from air may occur at rates that are comparable to or larger than inhalation uptake.” – Weschler CJ, Nazarofi WW, Dermal Uptake of Organic Vapors Commonly Found in Indoor Air, Environmental Science & Technology, 2014, 48, 1230-1237

“Air threshold limits are insufficient to prevent adverse health effects in the case of contact with substances with a high dermal absorption potential.” - Drexler H, Skin protection and percutaneous absorption of chemical hazards, Int. Arch Occup. Environ. Health (2003) 76:359-361

This can vary depending upon the type of isocyanate you are using and its volatility and any other constituents in the mixture, e.g. a solvent such as xylene.

Chris

You do not state which "isocyanate(s)" - it is only EH40 which gives a generic listing i.e. no CAS No covering all variants for a Workplace Exposure Limit.

If it is MDI then this particular substance and its isomers have a market retriction under REACH

https://echa.europa.eu/documents/10162/46cb2ae0-ee6b-4319-8604-b5b1d4a41d53

NOTE: this is applicable to the Consumer market where in the absence of adequate ventilation does require RPE even the Industrial and Professional markets may require RPE based upon application method/use.

An SDS addresses the mixture where supplied - the RPE requirement may not be related to the isocyanate but as Chris has indicated the solvent carrier - Section 3.2 where the hazards for the individual component substances (as 100% product) will show which constituents are contributing to the overall classification.

Example a prosecution from last year where a typical isocyanate solvent DCM was involved:

https://press.hse.gov.uk/2019/05/23/two-companies-fined-after-floor-layer-fatally-exposed-to-toxic-substance/

The opinion you have been provided would likely not be repeated as expert testimony in court - get professional determination of actual task exposure levels to work from.

From as below and specifically notes roller work. 

https://www.hse.gov.uk/construction/healthrisks/hazardous-substances/isocyanates.htm

Respiratory Protective Equipment (RPE) – you may need RPE where ventilation does not provide enough control – particularly in enclosed spaces if you are creating an aerosol (eg by some rollering work) or using products with significant amounts of TDI. Wearers should be fit tested where needed. It is particularly important to select the correct filter. For example, P3 particulate filters provide protection against spray mist but do not protect you from vapours. You will need the right gas / vapour filter for these. Change them at suitable intervals. Check with your supplier if you’re not sure.

I suggest you also consider health surveillance.

Chris

Security image "WiTY" - shame this was not for a different post